I'd recommend 550W. Here are some recommendations:
XFX TS 550W 80 Plus Gold certified Power Supply Unit
Seasonic S12G-550 550W 80+ Gold Certified Wired Power Supply
They^ are high quality PSUs and are relatively affordable
I'd recommend 550W. Here are some recommendations:
XFX TS 550W 80 Plus Gold certified Power Supply Unit
Seasonic S12G-550 550W 80+ Gold Certified Wired Power Supply
They^ are high quality PSUs and are relatively affordable