The Setup will use a minimum of ~400watts. Just to play it safe i would go with a slightly higher wattage psu. A 550w or even a 650w for overclocking and upgrades in the future. If not, then atleast get a good brand of PSU like a corsair, Antec, Seasonic
It's never good to run a power supply at close to full load all the time and when gaming it will put a strain on the psu and eventually shorten its life-span. Will a 500w work? Yes! Do i recommend using it? No!