550w should be plenty, however I'm sure many will tell you that Sentey is not the way to go.
"No , it's a very very poor power supply.
These are high quality
PCPartPicker part list / Price breakdown by merchant / Benchmarks
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($59.99 @ NCIX US)
Total: $59.99
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-17 18:33 EDT-0400)
or
PCPartPicker part list / Price breakdown by merchant / Benchmarks
Power Supply: Antec High Current Gamer 620W 80+ Bronze Certified Semi-Modular ATX Power Supply ($64.99 @ NCIX US)
Total: $64.99
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-17 18:34 EDT-0400)" ~SR-71 Blackbird
http://www.tomshardware.com/answers/id-2146756/sentey-good-psu-brand.html