Dell Optiplex - Recommendations Needed

24 to 8 pin is correct for 7040 only

but 7040 only supports 6th gen

7050 supports 7th gen

7060 8th gen

7070 8th/9th gen

it is better to choose 7050 because OP interested in 7th gen, and also easier to upgrade to Dell 360w or 500w psu to support 1660 etc.

most models on sale out there have the basic entry level psu which do not have 6 pin black PCIe for > 75 w gpu, so a psu upgrade is almost certainly needed to run 1660.  if just to run 1650, no need to upgrade psu.

1660 is better suited in an Optiplex MT.  SFF can only accommodate low profile gpu

finally to use standard 24/4 pin psu plus adapter, it needs to be MT too.  psu would not mount in Dell case.  OP needs a custom mounting such as double sticky tape etc to fasten the psu, or just leave it stand loose in case if PC is not transported.

Well, so that you can run Windows-11 ... I would suggest a refurbished Optiplex desktop with at least an 8th-Gen Intel processor (preferably an i7-model).

You should get the Tower model. You might need an wiring-adapter for the after-market Power-Supply. 

https://www.moddiy.com/search.php?search_query=dell&x=0&y=0

Also see:

https://www.dell.com/community/en/conversations/optiplex-desktops/optiplex-proprietary-8-pin-and-6-pin-pinout/647f8f68f4ccf8a8de077d92

I just gave my old Vostro-460 (same as XPS-8300) to my grand-nephew. Still games fine at 1080p. It was running a Zotac GTX-1660, and I had installed a Corsair-650 watter long-ago (runs it fine and stays-cool). 

@redxps630​ so, from what it looks like, I can get my hands on an Optiplex 7050 with an I7-7700 for a rough $100. With it being that, is that a 6-pin or an 8-pin? If it is a 6 pin, I need to buy a new adapter, as I only have 8 to 24 pin. I'd like to know ahead of time.

Online, I was told to purchase an Apevia 500W SFX PSU. They said/showed it'd be small enough to be inside of the case.. loose I think? But yes, I'd be buying a MT, not SFF or Micro. 

So, I should be perfectly fine to proceed with purchasing an Optiplex 7050, using an I7-7700, and a NVIDIA GTX 1660? I'd just need to spend about $40 on this PSU, and possibly a new adapter?

Also, what about an upgrade to an I7-7700K? I can never get a straight answer on having the unlocked. 

7050 has a white 6 pin socket.

Apevia is not a recommended name brand

you cannot install a standard ATX in MT case.  there is not enough room btn mobo and case floor to fit ATX psu

I recommend Dell oem 360w or 500w psu which would fit and you do not need adapter.

you do not need 7700K.  Optiplex bios does not support overclock of unlocked -k cpu.

7700k is often pricey than 7700

@AquosGold​ 

1. from what it looks like, I can get my hands on an Optiplex 7050 with an I7-7700 for a rough $100. 

2. Online, I was told to purchase an Apevia 500W SFX PSU. They said/showed it'd be small enough to be inside of the case.. loose I think? But yes, I'd be buying a MT, not SFF or Micro. 

1. Yes, those are cheap as they are now obsolete (can't get to Windows-11). See my post above. Windows-10 is EOL later this year.

2. As @redxps630 posted, something like a Dell-OEM or Corsair PS would be better.

@Tesla1856​ Corsair can get far more pricey. Is there any particular reason?

@AquosGold​

@Tesla1856​ Corsair can get far more pricey. Is there any particular reason?

They are built-better. They are more likely to NOT blow-up in a couple of years (and take-out your motherboard and/or video-card). 

They are known in the industry to be well-made and dependable. 

I suppose I can resort to one off of Ebay. I could surely get a Corsair 500W for under 50 that way. 

Thank you for the assistance, I think I'll go this route then. Just to be clear, I won't need to do any case modifications like some videos lead me to believe, correct? Or will I?

only SFX psu can fit loosely in MT case. regular ATX psu will have to sit outside case.  make sure you are aware of that before commit.

No, I WOULD NOT suggest buying someones old/used power-supply off of Ebay.

I do suggest you download the Service-Manual for any refurbished Optiplex you plan to buy. It shows the inside and anything you would need to know (without having the machine in front of you yet).

this is what 7050 MT looks like.  psu needs to be thin to fit in the space btn mobo and chassis