Re: PSU for 670
I run two 670's in SLi with a i7 3770k overclocked and 3 HDDs, it only pulls around 450W from the wall at full load (this was measured using a kill-a-watt). If you account for about 85% power supply efficiency it is really only pulling 380 watts DC. So even a 450 watt PSU can handle 670's in SLi. For just one all you really need is a 350 watt PSU. The new Kepler based graphics cards are very power efficient as is Ivy Bridge, you don't need insane PSUs for them like you did with the 480GTX and 580GTX.
When I switched from my overclocked Socket 1366 i7 920 and 580 SLi to the 3770k and 670 SLi it almost cut my electric bill in half.