If you've already got a 480 PSU, you'll be just fine. Im currently running the following on a 430 watt Antec TruePower...
A64 3200, gig of pc3200, two 160 gig 7200 rpm maxtors, one 100gig 7200 rpm western digital, msi dvd burner, tdk 48x cd burner, radeon 9800, about eight 80mm case fans, cold...