What 500 watt PSU, as we have explained
Not all PSU's are equal, I would take a 300 watt PCP&C over your average 500 watt.
Your average no name brand 500 watt PSU will not have enough 12 volt power to power a gaming PC, will only put out it's full power (if that) at a low temperature like 25
Most PSU's expisally cheap ones run at 40-50 degrees, which makes them drop almost all of their power