Yup. I've seen those stats. Amazing difference, even between cards of the same brand and memory. Some of those Geforce 128 mb cards score better then Geforce 256 mb cards.. Which goes to show that bigger isn't always better

And then there's the differences in ram type & size, processor type & speed, config, drivers.. Even if you take two supposedly identical systems, you might get two very different benchmark scores.
Problem is, you might get the best results with a Geforce on this game, but another game would prefer an ATI or a lower spec card then you have. Only way to find out if it'll run decent is to get a demo or borrow a copy froma friend and test it yourself.
And this is one of those reasons why I prefer consoles
