Buy you a quality 550 Watt at the least the difference in price will be very small and allow for a bit more head room I would even consider a 650 Watt to allow for future upgrades.
Seasonic, XFX, EVGA GS or G2 series are hard to go wrong with.
Any of these would be good or just get the same model but the 550 Watt but I would spend the little extra for future upgrades it's usually better to spend a bit more now then later buying a new PSU to make a large video card upgrade.
http://pcpartpicker.com/parts/compare/evga-power-supply-220g20650y1%2Cevga-power-supply-220gs0650v1%2Cseasonic-power-supply-ssr650rm%2Cxfx-power-supply-p1650bbefx/