I havent been concerned about the wattage, since most calculators shows about minimum 400w PSU need.
(bear in mind that my GPU is quite "easy" on the watts, compared to crossfire and GLI(?) cards.
I think it only draws between 10 and 20 watts? (might be wrong, cant find any data on it now)
but - probably the next upgrade will be a new PSU.
Might be a while though - just cashed in the Noctua cooler and a SSD.
Probably will change the HDD setup so I have 1x SSD for OS, 2x w.raptor for audio and single HSS for samples.
This will do something for the PSU as well - to now it had 5 HDDs...