You need a more powerful power supply IMHO. I recommend a bare minimum of a 650 to 700 watt for this rig and here is a list of great power supplies:
Seasonic - any model
Corsair - any model
Thermaltake - "Toughpower" series only
Coolermaster - "Real Power Pro" series only
PC Power & Cooling - any model
Silverstone - any model
Seasonic - any model
Corsair - any model
Thermaltake - "Toughpower" series only
Coolermaster - "Real Power Pro" series only
PC Power & Cooling - any model
Silverstone - any model