Toms E5620 pulled 220W at stock, 316W at 4.2ghz. Toms 280x pulled 260W. Not sure if you've overclocked at all, or if you're going to add a second graphics, but 48A (that load) would have those numbers just under 90% load for a 650W/54A, under 80% load for a 750W/62A. If you're going with a 2nd...