It's definitely the PSU. Coolermaster's PSU are pretty crappy.
What this really comes down to is how much you're wanting to spend. The XFX 650W 80+ Silver is a great PSU, and really cheap at $60 after rebate. However, the SeaSonic 650W 80+ Gold would be quieter (less heat produced), but it costs $146 with shipping.
Part of it is probably also due to the CPU fan, as that's not exactly the best one. I'd suggest looking at the Scythe Mugen 2 Rev. B as well.
I'd say that your best chance for a significant improvement in the noise is to pick up the SeaSonic PSU and the Scythe Mugen, if you want to spend $190. If you want to spend less than that, I'd go wtih the XFX PSU and the new HSF over just the SeaSonic PSU.
your componnent is very good but cm 650 gx is very bad chooise this psu after 480 w proudiuce siginificant ripple and noise T bad amper and bad voltag
for this very good componnent i sugest this psu so that recommended by toms and annandtech
Corsair AX750 http://www.anandtech.com/show/4011/corsair-ax750-80plus...
December 30, 2010
be Quiet! Straight Power E8 580 W
Cooler Master Silent Pro Gold 700