In my experience putting General Drawing Quality to 10 is more taxing than turning AO on. That is your problem.

I get 60FPS 98% the time with a 6970(@950), i7-930(@4.0) and only 6GB(1600) of ram.
Settings are as follows:
1920x1080
16xQ CSAA
GDQ: 8
BDQ: 5
Shadow: Highest
AO: Off
DoF: Off
Texture Quality: High
Texture Filtering: Highest