Hello.
I have a meaty, heavy Seasonic M12 500w. My system is: 2500k OC'ed to 4Ghz, 460SE, 6gb RAM, 1 SSD and 1 HDD, 2 120mm and 2 160mm fan. and a soundcard.
I plan on upgrading to a 7950, and plan on overclocking it. Most reviews would put whole system draw at around 400w when using a 7950...