How much faster is a Geforce 7600 GS than a Geforce 6800 GS?
That is no SIMPLE question…
Go to tomshardware.com and look at the comparison charts of the graphics cards, to compare FPS with different games:
This link has the most complete fair comparison I have seen.
Looks like the 6800GS is faster than the 7600GS. I happen to have had both cards in the same machine, one after the other, and I would concur.