volt mod a 7900gt and youve got a killer card for the price. 7600gt is a great card aswell.
Or a 7900gtx - the higher memory speeds (AKA 7900gto) But with some overclocking on the ram you get a 7900gtx for about 140$ less
In reality any of the 79xx series cards will play any new game great. whether it be a 7900gt, or a 7950gx2. Use your alloted budget to help you decide!'
EDIT: for the price of the 7950gt, you can get a better card, the 7900gto, its has higher stock clock speeds, and about the same mem speeds for a few $$ less and is a proven overclocker. Reaching and exceeding 7900gtx speeds.