Kaoyaku, Like worhsipme said, In order to give you the best advice possible, we need to know what resolution//size monitor youre using, ram amount and yes the games you play. Some are more CPU intense and others are more GPU intense.. With that being said both of these can be hindered by playing the game on certain screen resolutions.
As far as the best cards within that price range, I'm really getting fond of the ATI Radeon 4870 1GB. You can also purchase a GTX 260 core 216 which is just studly but equal to the ATI. Really, im sure a 4850 wouldn't be too bad or a 9800GTX but in all honesty, I'd go with the 4870 or the GTX 260.
EDIT: The reason im even recommending the two cards I do is because I know I'd feel extremely happy with my money spent on either one. Its just with my current set-up I've got to figure out which one works for my individual basis.