I have a similar setup. I've been kind of frustrated getting steady high fps, toned back several settings and gave up. It's normally pretty good, but on the quick SA(usually worse than normal maps) test I was getting ~50's combat 85 vsync(out of 100hz monitor?!)
I think I have all the C# state options in bios turned on, though many OC threads say leave them off. Otherwise I do 10% current capacity and whatever asus "optimized" voltage phase control is.
2500k@4.0 OC by all cores(be careful, voltage seems to be the only way to kill the sandy bridge chips, and I seem to do 4.3 stable at 1.17v
gtx460 evga
p67 asus
8gb 1600 corsair
win7x64 dx9
1280x1024 using ccc 3, sharp shadows, vsync(i hate cooking my card at 500fps in the menu), and physics on 3.
nvidia crysis.exe settings:
AF and AA = app controlled
AA transparency = off
single display
power= max performance
anistropic optimization = off
quality = quality
negative LOD = allow
trilinear = on
thread = on
triple = on
vsync = app control
Hope this helps some how.