I can do 1680x1050 with everything on high without any AA and it's pretty playable. It runs better with SLI enabled and shadows turned to medium. Everything else I leave on high. Even then I only get between 25 and 50FPS. It usually averages in the low to mid-thirties.
I'll try turning shadows to medium
maybe that'll get playable. I'm fine except at random times and it slows.