For anyone saying 700W is limiting future expansion needs to really look at the actual wattage. Even a Quad-core SLI machine isn't gonna pull more then 600 & that's with like 4+ HD's & dvd-roms, Fans, lights..etc. If you get a quality PSU Brand example: Corsair 750w TX, PC Power & Cooling, Silverstone, Enermax, even thermaltake's high-end is good & plenty more. 1K watt PSU's are for simply show, nothing more.

CPU's are being made to use less wattage, not more. The only thing to worry/consider is the GPU's involved, & quite frankly if you don't SLI/CF than 1K is wasting wattage. For a system you listed above, the Corsair 750w is $110.00 @ newegg.com & will last even for future builds.

Overall welcome to the forums & congrats on the build. The 280GTX is the best bang for youre money, the 4870 1GB is the best single card under $300, anything more & you should just be CF 4850's (in +1 solutions) & calling it a day. The 9-series is last season as well. Raid 0 over Raptors, more space less money, & great performance. Tom's Hardware does great things for reviews & card(s) of the month.