Power Supply:XFX TS 550W 80+ Gold Certified ATX Power Supply ($64.99 @ Newegg) Total: $64.99 Prices include shipping, taxes, and discounts when available Generated by PCPartPicker 2014-09-18 23:00 EDT-0400
A 500w psu seems like the best bet to me since none of your components are very power hungry. 500w is probably more than the recommended but its better to be safe and this will allow for a little bit of OC'ing for the 270x.