Go with the Q9450 instead of the Q6700. It's newer technology as it's based on the 45nm process. I think 4GB (2x2) of ram would be more suitable for the Quad and it also gives you the option to upgrade to 8GB in the future. As for the GPU, I think you'll be better off with the 8800GT in SLI as theres not much difference in price between the 9600GT and the 8800GT.
Edit: I just read that you'll be overclocking, So in that case, go with the 8800 GTS (G92) SLI. It has better cooling the both other options leaving more headroom for overclocking.
Maroc.