I used the PSU Calculator for my build and it said I needed 900w and recommended a 950w psu. So I ordered a Corsair 950tx to take advantage of a great sale.
My build:
Mobo: P6X58D-E
CPU: i7 930
RAM: 6 GB DDR3 1600
GPU: 2x GTX 480 SLI
HDD: 1TB 7200 SATA 6Gb/s
ODD: DVD
Cooling: Corsair...