Play games and such... Right now I'm at 1280 x 960 res. I don't know what else you need to know about what's in my computer. I just want to know what's the best video card I can get that'll work smoothly with my processor.
Your processor is fine and your resolution doesn't require a high end video card. It's your PSU that is more likely to limit your possible GPU selection.
In general for your resolution an HD4850/HD5750/GTS 250 should perform very well. The most you should consider is probably the HD5770 unless you plan on upgrading your monitor in the not too distant future.