It's sad to see such a great game with no players...
Anyways, you should be able to play the game at 800x600 2/2 or 3/3 settings if that's fine with you, I tried the demo on a P4 3.0GHz with a 6800XT (a lot slower than your 6800GT) and I could play well at 800x600 2/2, the 1.1 version of the game should also have some extra optimizations. What bothered me the most is that you can't turn of post-processing and HDR, they would definitely speed things up for lower-end machines and they aren't gameplay-critical features anyway.