One thing to be aware is not all psu's are equal..
one companies 500w is not equal to another's 350w psu..
I like to stick to Antec, OCZ, Zippy, PC P&C, Seasonic, & Enermax psu's..
My current favorite are the Seasonic, OCZ & PC P&C psu's..
Probably cost wise a 500w Seasonic should do...