The 600w PS will be fine for your initial build. As for getting a larger PS in the future it depends on your total sum of devices (IE # of hardrives, CD and DVD drives, USB, Firewire, memory sticks, and PCI cards). From what you have listed your 600w PS is in budget with adding another card to do SLI but if you have alot of other stuff the 600w PS could be hammered. For example if you run (4) 10000 rpm harddrives in a raid 10 with two DVD burners, printer, two external harddrives, and a soundblaster PCI card you will probably need to stepup your PS. And if you plan to overclock a system your power goes up again.