At stock, the X1950PRO is more powerful, but it can't overclock much. The 7900GS on the other hand, can overclock really well, from what I heard, and will beat the X1950PRO stock.
yea i know right the one card that i buy to temporarily replace my old 8500gt doesnt even have the requirement specs to meet bioshock, so that ****ed me off haha.. anyway im leaving in like an hour to go get the eVGA 8600GT SuperClocked... so hopefully it holds up until I get thge cash for a frickin 8800GTS