I agree with BigFeet, you need a good PSU. 600W does not mean it can also deliver the power you need as it is the total of the whole supply. Just do not go overboard as well as these SMPS (switch mode power supply) need to run at a certain output to be efficient which is usually at 75% or better. That means if your overall total power consumption is about 800W (Video card, motherboard and everything connected to it) you should not go under 1050W.
However, with this kind of power, efficient cooling is a must as well (no obstructions in the air paths)...