Game effects quality, Post processing quality, and Water quality have very little influence on the performance.(on my second rig i have a 7600gs and i see no difference in FPS when i set these to low or high). i found that Object quality has a huge influence on the performance.

I got physics quality on high on this rig (7600gs, E6300, 2gb) and texture quality too.
It's only running 800×600 tho but still, it looks very good.
I didn't expect it to run any better on a 7600gs.

I think it's strange that the high end cards don't perform that much better than most mid-range cards.. i mean, i haven't run this on my 7900gt yet, but the beta ran pretty well on it with most settings maxed out @ 1280×1024. (avg about 25fps i'd say, i haven't seen a 8800gtsdoing MUCH better than this)