Get 6600 GT, it is not that perfect, but play every to day game at high/ ultra setting, missed AA of course.
Save some $ for the next mid range VGA generation, will heat 6800GT at least, imo. See, 6600 GT heat 9800 Pro/ XT.
My Rig
Abit AV 8
AMD 64 3000 939
Corsair value 2 x 512...