Well, I'm upgrading from an E6750 to a Q6600 in the next day or so, I hope to see a significant improvement in performance now my GFX isn't so choked by the struggling CPU.
I used to play with an E6750 stock and 8800GTS 320MB. Game was playable at 30FPS on lowish settings (med textures), though often dipped to 17FPS when things got busy, but mostly OK.
I then upgraded the 8800 to a GTX280. Now it's about the same performance, but with the graphics quality turned up - that is, textures to high, filtering on very high, though any changes in view distance and car densities and it struggles still.
I managed to get my E6750 to 3.6GHz for a short game and bench, and it played buttery smooth on higher settings, so I'd found the bottleneck for sure. Unfortunately the E6750 and my board wouldn't go beyond 3GHz rock solid stable, and I didn't have much time to mess around trying to improve it.
Now going to a Q6600, I hope to see a leap in performance like the OC did. With any luck the quad will also manage 3.6, but this time stable with a bit less fuss. The VID is significantly lower than the E6750's.
I'll update this thread with results.
PS: Multiplayer sucks! If only you could have decent servers with no cheating. Twas OK at first but now it's silly!