A Q6600 at 3.2 or above is still excellent for gaming. The 5750 is probably inadequate depending on your resolution (which is...?). The largest single-component upgrade you can do is an SSD, so I think combining a good heatsink+SSD would make this build better.
If your monitor is large, then maybe scrap the SSD for a better/second GPU.
Thanks for the replies! My max resolution is 1680x1050.
SSD looks a very nice suggestion to me, but also the cpu cooler+ oc the processor seems a very good one since my cpu is running at 2.4ghz at the moment.
I never oced a processor before tho and i've always thought it was something dangerous to do.
What about the power supply? Should i get a better one? Mine is pretty old...