The OCZ ModXstream is $40 after discount/MIR on Amazon. A great deal on a decent quality PSU that is more than sufficient for your PC. I run an HD6950 on a Seasonic M12I-520; great PSU but a bit out of your price range.
Hmm I can't seem to find it. I see the 500w 600w and 700w options, but I don't see one for 40 dollars. Could you possibly link me to one? Thanks!