If your system used to run fine with that 600w psu how is it underpowering the gpu? No doubt it is a cheap psu and it could be the problem, your best off trying another power supply unit because it could be on it's way out, that's the problem buying cheap psu's should always go for good quality will save you money in the long run.
ya it came with the "bundle" i bought though =(, i didnt get to pick it ....... but I dont really have another PSU, that is BETTER then this one........ thats the problem.......should i just invest in a new one?