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
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.