get the q9300 and oc it, yes most games work on vista as of sp1
get a better gfx card, 8800gt maybe its a little more money and much more power and whats with the heavy duty box? box doesn't protect your components bubble wrap and foam do and glance at xigmatek for air cooling
figured with ncix links
nvidia is simply making better GPUs right now, might change in a couple weeks
pixel pipelines shader clocks memory and memory bandwidth core clock, but the easiest way is took look at bench marks on various tech sites
Id say depends on how much graphics power you want/need. 2 8800GTs in an SLI (@ ~$350 total) perform much higher than a single 8800GT (or, for that matter, any single-gpu ATI card). Now, if you are willing to wait until the 17th of this month, Nvidia is introducing the new GT200 series cards, the GTX 260 and GTX 280. Though rumored to cost $449 and $649 respectively in US Dollars, even the lesser of the two should produce favorable results compared to the SLIed 8800GTs. Though, money-wise, the performance advantage might not outweigh the additional cost of the new cards.
In any event, I would wait and see who comes out on top in the next couple of weeks as both ATI and Nvidia will have their next-gen cards on the market. This decision will also effect your motherboard choice as SLI is currently only available on Nvidia chipset-based boards. Crossfire is offered on both Intel X38 and X48 chipsets as well as others. Stay tuned...
I'd be weary about the Core 2 Quad Q9300. Though it is Yorkfield (45nm), it features only 6MB of L2 cache, whereas the older 65nm Q6600 and Q6700 both have 8MB. I read an article in Custom PC last month about the Q9300 and they concluded it was not on-par with the chips it replaces, namely the Q6600/6700 because of the lack of L2 cache. Now, the newer Q9450 has 12MB and should outperform most other quads under it. Plus its Yorkfield 45nm process should translate into less heat.