So in the case of a P5K + Q6600 + 8800GT system (like mine), is it better to upgrade the GPU rather than OC the Q6600?
I play mostly RTS games like C&C3, WiC, RA3 and my display is 19" with 1280x1024 max....
Originally Posted by Simmity 
Overclocking a cpu will increase you're performance in games, however you will only see big performance differences if you got a fast gpu in games. Crysis is optimized for multi threading. But the cpu is often "waiting" for the gpu to render. The more fps you get the faster a cpu must work.
For an example: An 8800 GTX requires a dual core 3.0 Ghz to work at maximum speed. Now think about putting 2 9800 GX2 in sli with a dual core 3.0 Ghz and you can see that overclocking the cpu will have great performance increases.
Try an other application to test performance. You might want to run pcmark at standard speeds and then at overclocked speeds. Or just unzipping/unrarring a Large file.