It depends how high-end your system is. You may just get away with the
Antec trio 550W if the rest of your system requires little power.
Although i recommend:
Antec trio 650W
OCZ GameXtreme 700W
Remember - You can Never Have too much power - More is better.
If you post the rest of your System we can pick an Appropriate Power supply unit. Problem is alot of people forget about how much power the newer Technology needs to run untill nothing works or they recieve errors.