all i would do is bump up the wattage of the power supply. look at a 650-700w unit to be safe. it not the total wattage that the issue it the 12v line. the amp rating on the 12v line has to run both the cpu and gpu. your better off making sure you have some head room for that 12v line. you dont want to load a power supply to 80 percent or more of it rated load. most power supply there sweet spot is 50 percent rated load.