Dell 8400 Video Card Upgrade

The HD 4830 will be fine on the 350 watt power supply.  This Sapphire seems to be the most popular one on Newegg and has a good cooler on it.  It is not available right now from Newegg so I linked to TigerDirect.  Newegg has another model but it is not the Dual DVI version or the most popular one with 257 reviews.  ATI has a new card coming out this month called the RV740 (HD 4750 or HD 4770).  It's performance is suppose to be between the 4830 and 4850 and may be worth waiting for at a cost less than $100 which will then probably knock down the cost of the 4830.   However, having said all that, you are not going to get the best performance out of these better cards as you would with a Core 2 Duo or Core 2 Quad CPU.  The P4 will definately drop your frame rates down compared to what it would be with the better processors and you really need to get another GB of Ram.  Nevertheless, just about anything is better than the X300.

I have a similar rig (3.2Ghz P4 with the 350W PSU), except I have 3GB RAM and was using an ATI X800 XT as my graphics card.  I needed an upgrade because the X800 series does not support shader model 3.0 and I wanted to play Mass Effect and BioShock.  I was able to upgrade to the ATI HD 4770.  It has better performance than the 4830 and lower power consumption because of the 45nm architecture and the use of GDDR5 RAM.  It works great.  I haven't tried CoD4 yet, but it runs Mass Effect and Left 4 Dead well at medium to high detail settings.  I very rarely notice some lag or glitch in the game because of the slower processor, but they are VERY playable.  The 4770 does not get hot in my case and has shown no signs of taxing the PSU.  In fact, I read that it only uses about 20 more watts than the X800 did at peak vs. some of these new cards that can use more than 100 watts more.  It is a little hard to find now, but I have seen it in stores online ranging from $99-$120.  I would definitely recommend it.  Good luck.

Thank you very much for the suggestions. Thanks to my PSU failing my lack of power issue was solved before I purchased a new card. I purchased and installed a 550W PSU from PC Power and Cooling. I have since purchased a Sapphire HD 3870, yes it's older and yes it does draw a lot of power, but it stays cool and has plenty of processing power and I got it from Newegg with free shipping for $65 plus a $10 erebate. All my games are extremely playable now with 60-70 FPS. I only notice my lack of a powerful CPU when loading Call of Duty 5 levels, it takes forever, but in game is fine. Thanks again for your help.