Have you tried tweaking your setup at all? I mean, yours is far better than mine (check sig), but I get a solid 45fps even in the largest city with these settings:
(MFD's split to second monitor)
In my Nvidia Control panel I create the game profile then leave everything default except these values:
- anisotropic filtering: 8x
- Gamma correction anti-aliasing: On
- Anti-aliasing mode: enhance application setting
- Anti-aliasing setting: 2x
- Maximum pre-rendered frames: 1
- Power management: Max performance
- SLI Mode: Alternate Frame Rendering 2
- Anisotropic optimization: On
- Negative LOD Bias: Clamp
- Texture Quality: High performance
- Trilinear optimization: On
- Threaded optimization: On
If you get MFD flicker from using Alternate frame rendering 2, use the setting of 512 or 1024 every frame, that gets rid of it.
What OS are you using? If you have Vista/Win7, try running in windowed both with the Aero interface turned on and off. Sometimes one performs much better than the other.