1)Motherboards support different cpus at the time of their release - i think there are alot of factors here.
2)The P35-DS3R is one of the newest and best performing mobos with support for 1333fsb and the P35C-DS3R model supports DDR3, but that wont be mainstream for at least 2 years i doubt.
3)Upgrading you mobo/cpu requires a clean reinstall of windows. Some people recon you dont need to, but i wouldnt suggest trying to simply switch motherboards over.
4)I like vista, but there are still some driver problems, and problems with older versions of programs. I suggest reading reviews.
5)That system isnt to bad a price for what it is - although i could get those parts for about $100 cheaper. Also, there are better parts you could get for the money.
So if your planning to put you 7900GTX (which is faster than that 8600 btw) then there is not use paying for another card.
Try this site -
Loading.. there pretty good and cheap.