That IS . . . a LOW 3DMark06. Both processor and VGA clock settings affect it.
It just seems way too low to me. I only have a single 8800 GTS 640MB card with my C2Q-Q6600, and I got 11,500 3DMarks.
If you want to over-clock the VGA, get both ATI-Tool and RivaTuner -- install both.
Give attention to detail, or you'll crash the system in the process, but ATITool will test both GPU and graphics memory clocks automatically at ascending settings. You're best to do a little research at some forums and get a handle on what the maximums are likely to be with your 8600 card, then fix ceilings in ATITool.
Once you have that range, you can choose settings within the range using RivaTuner. If you OC the card through ATITool, I suspect that it will lead to instability. And RivaTuner allows you to choose default settings that are recorded in the system registry and set at boot-up. This way, you don't have to flash the VGA BIOS with the chosen values.
I think that OC'ing my 8800 GTS from 850/792 to 875/900 bought me 1,000 3DMark points in 3DMark06. I could be wrong, but I think it was so.