Do I need a PSU upgrade?

It's a good idea to upgrade the power supply if a high-powered video card like the GTX 970 is to be used.

If you do elect to replace the power supply, please note that only power supplies of 5.9 inches or less in length will fit.

Are you absolutely sure an upgraded psu would be necessary? I built a "test" pc with the same parts as my pc on pcpartpicker and it says its recommended that the psu must be at least 380 watts. Im trying to save money where I can so it would be in my best interest to not upgrade the PSU. Maybe a mini itx gtx 970 would be better since they use less power?

If your power supply has a six-pin connector, it may be adequate.

here is my .02 on the XPS 8700 power supply.

If you are going to spend $600 to $800 on the XPS 8700 desktop, and then spend another $400 to $500 adding an SSD and the graphics card, why trust it on a power supply that is marginal at best and compared to other units on the market is worth about $25 USD

You can get by without upgrading it, but my opinion is, it will fail or it might be intermittently unstable.

for $50 to $100 you can get an good to awesome PSU that will provide enough output.

PSUs are not something you want to load at 100% and run for a period of time.

So is it absolutely necessary? No. 

Is it recommended? Yes.

380 watts is wrong.  The card will use 300W from the aux power connections and 75W from the PCI-E connector.  Do you really think that the entire rest of the computer will operate on 5W? Its wrong to think of a computer that only uses 12v on a single rail and all the other voltages are free.   You need 150 to 170W on the 3.3v/5v rails, then 15W - 25W on the +5VSB rail  which is 195W. And with only 80 percent efficiency you need 245W Input to get that 195W.  Typically you need 48 Amps OR MORE on the 12v rails Which is 576W. At 80 percent Efficency that means 720W X .8 =576W

This is why I recommend a Corsair CS750M is a Minimum. For SLI 2 cards like this I do not recommend anything less than an RM1000  power supply.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139057

 ATX is Wrong and inadequate.  You must use EPS12v 2.91+ certified power supply.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139061

http://www.amazon.com/gp/product/B00K85X2A2/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Would this PSU fit?

This is why I recommend a Corsair CS750M is a Minimum. For SLI 2 cards like this I do not recommend anything less than an RM1000  power supply.

They're saying 550 watts; I didn't realize that the card itself drew 550 watts!

With that kind of power consumption, I recommend moving the innards to a gaming chassis with better cooling.

They're saying 550 watts; I didn't realize that the card itself drew 550 watts!

Who is saying 550 watts?  The GTX 970 doesn't draw 550 watts. max power is 213 watts during these tests with average power consumption at 168W, details how and what is behind these numbers are at this link.

http://www.techpowerup.com/reviews/MSI/GTX_970_Gaming/

GTX 970 Power consumption is less than a GTX 770.

MSI says this card needs a minimum 500 watt PSU, and that's for the entire system so a high quality PSU like the seasonic or the EVGA is more than enough.

http://us.msi.com/product/vga/GTX-970-GAMING-4G.html#hero-specification

Cooling is fine. We have a GTX 770 overclocked in one of our XPS 8700s and temps are decent.  I moved the HDD up to location 2 and removed the HDD cage for better front air flow but extended gaming does not heat it up.

Several examples in this thread. .

http://en.community.dell.com/support-forums/desktop/f/3515/t/19611037

Who is saying 550 watts?

The specs for one card offered on Newegg say 550 watts, which presumably is the output of the power supply.

Cooling is fine.

It was my understanding there is just a single 92mm chassis fan, which may be able to deal with 250 watts, but (I would think) not 500 watts.

168 watts is not what the card draws.  If it were then a much smaller power supply could be used.

Thats only 14 Amps on the 12v rail. If it was that low an ancient ATX power supply could handle this.  EPS12v Specifys a single 12v rail that can exceed 450W which is 37.5 Amps. 

75W from the slot and 150W from the Aux power = 225W aka 150 to 225W range.

You don't operate a card in a vacuum with a single 12v supply for EVERYTHING in the pc.

The 3.3v/5V rails need 150 to 170W

The CPU uses around 90W

The 5VSB on newer Dells is 20W or 4 amps.

550 - 190 - 90 = 270W and thats not taking the other rails into consideration and its assuming 100 percent output.

750 X .8 = 600W

550 X .8 = 440W

 The EVGA Super Nova 650 is $84 and the CS750M is currently $99

I'd much rather pay $15 more for 100W more room and EPS12V 2.92 certification.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817438026

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139061

In general we agree better power supplies are good, however your numbers don't add up.

168 watts is not what the card draws.

I guess you did not read the article.  They tend to do a fairly good job, so I think I'll trust their test results.

And, If you read what I wrote, and read the review, 168W is "average" draw, and for this test "average"  is defined as follows. 

• " Average: Metro: Last Light at 1920x1080, representing a typical gaming power draw. Average of all readings (12 per second) while the benchmark was rendering (no title/loading screen). In order to heat up the card, we run the benchmark once without measuring power consumption.
• Peak: Metro: Last Light at 1920x1080, representing a typical gaming power draw. Highest single reading during the test.
• Maximum: Furmark Stability Test at 1280x1024, 0xAA. This results in a very high no-game power-consumption that can typically be reached only with stress-testing applications. We report the highest single reading after a short startup period. Initial bursts during startup are not included, as they are too short to be relevant."

www.techpowerup.com/.../25.html

note that Maximum was 213W.

Let's tally up MAX loads on a typical XPS 8700 system.

i7 4790   84 watt Total design power
MoBo, 50 watt based on other similar Z87 chipset boards. I don't have a reference for the 8700 mobo. 
RAM - 10 watt
HDD - 20 watts at startup, 10 watts after spinning
HDD2 +20W
SSD 5W
Sound Card - 10W
Wifi card 10W ?
ODD  30W when burning a DVD or BluRay. Less than 1 W idle,
case Fan 3W
CPU Fan 3W

Rough total  250 watts MAX without a graphics card.

Again MAX.  these are Max power load of each of the parts. it is hard to get all these parts to draw MAX power and nearly impossible to get all of them to draw max power at the same time.

Again, referencing the article, and "max Power" being the highest sustained load during a synthetic stress test 213W is the MAX power of the overclocked MSI GTX 970. Add this and you have about 460 watts - maximum power draw.

A sustained high level is closer to 350 to 400 watts when pushing a system as hard as possible during real work or gaming,  which is why you will find several that are able to run a GTX 970 with the stock PSU. 

So even at MAX power, this is only 75% of a 650W PSU, and closer to 55% to 60% during very heavy gaming.

My point?

 A Seasonic X-650 is overkill for any GTX 970 card and any (reasonable) combination of components in the 8700 case. 750W even more over kill. Anything above that makes no sense.

Your theory would hold water if computers operated from 1 12v supply and ignored the 3.3v and 5v and 5VSB rails.  But the truth is that computers are not Graphics cards with a single 12v rail to worry about. Current readings should be measured by a scope thousands of times a second not 12 times per second.  There are spikes on cards like this that go up to the 300W range.

There are many posts from people who had a 350 or 375W DELL power supply that replaced it with a 400 to 600 W supply and with a card with similar 150 to 225w power profile would not POST let alone turn on.

Power supplies should be chosen by SPEC and Warranty not price.  I guarantee you that cheap $20 diablotek and similar 550 to 650W power supplies that are ATX NOT EPS12V 2.92 will fry everything in short order.  You can do $99 overkill and not Kill your motherboard and everything else and it will work and keep working or you can save $10 to $20 and lose a fortune in blown up parts.

Speedstep, you seem to be challenged reading what I wrote. Please refrain from stating things I did not write. Please start reading more carefully. 

I have never suggested a cheap diablotek or any of the dozens of junk PSUs on the market.

Let me repeat it in a font size that is perhaps more readable.

A high quality 650W PSU is overkill for an XPS 8700. It is what I have in my systems, but it is overkill.

However, with a high-end, high power draw graphics card, a PSU like this is actually not a bad choice.  why? Because the PSUs are most efficient between 40 and 60% of their rated load, or with a 650W system, between 260W to 390W of load.  Convenient in that is around what an XPS 8700 with a high end graphics card like a GTX 770 or 970 pull when loaded heavily during gaming. 

The seasonic has some of the best voltage regulation in this power range,  and it fits into the cramped XPS 8700 case.

Also, please spare us the rant on EPS12V 2.92 being a requirement. Desktop systems do not require this spec, it is a server spec and a high-end workstation spec for dual CPUs and multiple graphics cards. The XPS 8700 OEM PSU doesn't meet EPS spec and while it doesn't hurt, it is not an absolute requirement 

Besides the ATX 12V version 2.x and EPS 12V 2.9x specs have essentially converged to the point where the high-end PSUs meet both simply by providing some additional cable connector options.

For example, the Seasonic X-650 meets both ATX12V V2.3/EPS 12V V2.91 as do most of the high quality PSUs

note: you mentioned version 2.92. the update from 2.91 to 2.92 adds clarity for connectors on 850 watt and higher PSUs so it doesn't really apply to a 650W system.

One final note:

There are almost no reviews nor independent tests of the Corsair CS 750M. Perhaps you can comment on why you recommend it.

The Seasonic SS-650KM is $119 on newegg.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817151088

 From the Label on The unit it DOES NOT MEET EPS12v 2.9 ,2.91 or 2.92 See Spec changes table below.

Using a single spec WATTS ignoring the underlying spec is misinformation at best and harmful at worst.  A CX430 or CX380 will not meet EPS12V minimum spec for +5VSB

 4.0 A / 4.5 A peak of +5 VSB is required for power supplies in systems supporting ACPI S3 power state; suspend to memory.

This is where "waking from sleep problems" occur or not.

Power rails are as follows:
•+3.3 V  
•+5 V
•+12 V
•–12 V
•+5 V standby

ATX is not acceptable and hasn't been for years now.  Reason being that the maximum current on any 12v Rail for ATX is 18 Amps. There are many vendors out there who fake specifications including the brand aka (Counterfeit Corsair for example) which leads vendors to say that they do not warranty parts that were not made by them.

If you spec a 750W or 850W EPS12v 2.92 supply this guarantees the 150 to 170W on the 3.3v/5v rails.   Power supplies with these specifications tend to be $90 to $150.  Depending on vendor and on sale or not.

When you put wiggle room in there you setup the mindset that Price is the spec and watts seals the deal and say ATX is fine and EPS12v is optional you find $19 to  $49 power supplies that are fake, have no over voltage or over current or true UL certification let alone 80% Gold efficiency.   Taking that risk at best you get a supply that doesn't work and at worst you get a motherboard fire with a loud pop/bang! and then everything is fried. 

I don't see testing that shows the voltage and current on All the critical rails including 3.3v, 5v, 5vsb, ATX12v(4pin), EPS12v(8pin) via amp probes and scope to graph all that is going on.  I see testing based on only watching what is happening at the AUX pci-e power connection of the GPU.

I see several recommendations that have 120w or 130w for the 3.3v/5v rails and less than 4A for the 5VSB.  This is clearly NON COMPLIANCE with EPS12v 2.92 spec.  EPS 2.8 specifys 3A for 5VSB.

My numbers are not wrong nor are they "off" they are codified in the EPS12v Specification.   160W for 3.3v/5v rail, 20W for the 5VSB Rail, More than 240W aka 20A for a single 12V rail.  If you look carefully even the Dell 305W power supplies have 150W and 20W. The spec bumps the 5VSB up to 6A for larger power supplies.