Here's a suggested parts list I did for Wheezy last week. Prices have probably changed, but this would be a pretty good start. Pick your case, the P182 was his pick, then add your monitor and sound stuff.
So, here's my suggest list: (including sources for cheapest price, no MIR's included)
Antec P182 - $122 - NX Source
Corsair TX750 - $125 - NCIX
Gigabyte EP45-DS3R mobo - $134 DirectCanada
Intel Q9550 - $370 Anitec Q9650 available soon for ~$600
Mushkin Redlines 4GB - $107 NX Source
Western Digital 640GB Drives x 2 - $73 each Compu2000
OCZ Vendetta 2 - $40 NCIX
4870x2 - $609 NCIX
Vista - $100
Gaming KB and Mouse - $125
Total with Q9550 - $1838
With Q9650 - $2068
Add $50 for assembly.
The Gigabyte boards are good overclockers, easy to use. You could put a Asus P5Q Pro in for $5 more, or a P5Q Deluxe for $65 more.
Prices obviously have the potential to be matched or beaten in some areas, I just pulled this stuff off NCIX. This is for a more compact design, using the Sonata III case, which I'm a big fan of. The only real drawback is that it can't handle video cards that extend beyond the motherboard, and the power supply isn't multi-GPU friendly. But case airflow is absolutely fantastic, and it's a very solidly built case.
I have yet to find a gaming keyboard I actually like better than my cheapo M$ Comfort Curve 2000 keyboard, although that's entirely subjective. One of the extra fans is to replace the godawful tri-cool fan the case comes with.
i7 2600K | ASUS Maximus IV GENE-Z | 580GTX | Corsair DDR3-2133
I forgot i will also be needing an operating system. On my pc right now im using xp and i havent really tried vista out. Should i stay with xp or should i get vista? Does it really matter anymore?
It matters, only in the respect of learning the little changes from XP. Most of the issues are ironed-out. You'll be able to take advantage of 4 or more GB of RAM(with VISTA/64..Home Premium recommended), but you'll also use a lot more of it than XP. If you want to be able to play new and upcoming games, the way they were meant to(DX10), then VISTA is a must.