Go with the q6600... you probably want a "gaming beast"... not a "gaming beast that will one day be such a beast because i have an e8400 because i'm waiting for the new cheaper 45nm quads to come out etc."
Also pick up this for your cpu as a cooler
Newegg.com - XIGMATEK HDT-S1283 120mm Rifle CPU Cooler - Retail
Since the q6600 your ordering does not have a stock cooler...
ALSO! if you do want a beast of a rig... Why not go for 9600 gt 512 in sli? It is cheaper then the 8800 gt 512 in sli AND! performs better!
If you are now into the idea of the 8800gts g92 then that is fine... There is nothing wrong with it. I just suggest that if you do go sli, go with the 9600 gt 512 x2