Replace the psu to a 550-600W unit from corsair, seasonic or antec. I recommend the corsair TX550M or corsair tx650 v2 or seasonic S12II 620
Everything else seems ok
I agree with this - that power supply is overkill and I'm not sure about the manufacturer. I'd drop the expensive peripherals for a better case from NZXT or Corsair, and then replace the 660TI with the Radeon 7950. The mouse mat isn't needed either - you're just spending money needlessly there.