I am happy with my three year old rig:
3D Mark Vantage: 16'591 overall score
3D Mark 11: P4642 overall score
My rig:
C2Q 9550@3.4GHz
ASUS P5Q
4x2GB DDR2 800MHz Corsair XMS2 RAM
0815 500GB HDD
ASUS GTX560Ti TOP @900MHz
1680x1050 screen resolution on old 21.5'' Apple Cinema Display
I did not install the patch yet. But before CloD was very playable with some adapted settings (not everything maxed out...) with about 20-30 FPS over London and the usual slow downs when the skies are busy
