8800 gtx is only noticeably faster than the GT on high resolutions.
If you play on something like 1280x1024 the GT is perfectly fine.
The Q6600 is a good CPU but if you're getting one of these then make sure it's a G0 stepping, as those have the best overclocking potential.
A Q9300 would also be an option. Should be about the same price, and it's the Yorkfield core, so 45nm die shrink of the core used in the Q6600. So that means less heat, better overclocking. It also supports SSE4.1 which speeds up a few programs considerably.
However these new quad cores were only just released I think so you might have trouble finding them at the moment.
Can't help much with the Case but considering it's a Lian-Li it should be good 
Likot Mosuskekim, Woodcutter cancels Sleep: Interrupted by Elephant.
