the corsair 620 watt is a real good one that can power your system. I have a 550 watt and im powering a 8800gts, p5n-e sli, quad core, 2gb ram, dvd drive, 2 HDD's, watercooling, 3 120m fans, 1 80mm fan.
yup just like ceewi1 said and i said, 500+ is just a basic requirement but, any pushing of the computer or overclocking or extra fans and depending on the case could even raise the recommendation of the voltage