500w is pushing it. if you go here,
http://www.extreme.outervision.com/PSUEngine
And put in your video card, cpu, ram, hd, you are at 403w, so at 500w and full load, you would running at 80% of your psu and thats no dvd drive, fans, leds, anything. you would safer at 650w then you are only at 60% max power usage.