Hi.
Flanker, your PSU is enough! You can easily overclock your 2500K to 4.5 Ghz, almost not touching the voltage adjustment. I am very ecsited to see, how much improvment you can get if you overclock you CPU on Clod. I still wait the Asus 7970DCII version of the card! Here is a link to
X-Bit Labs article about power consumption and overcloking CPU. A mid-range overcloking doesnt increase the power draw much.