You'll be pulling
a bit over 400W from 570 SLI at full load. Factor in maybe 150W for the rest of the components, probably closer to 200W if the CPU is stressed to max as well. So you've got about 600W absolute max power draw, usually less. That's not counting for DVD drives, usb devices etc... but they're marginal anyway.
It's a quality unit - I wouldn't worry, especially if it's still new.