650w even in a cheap PSU should be more than ample to run your components, as long as it's not prone to severe dips in voltage supply. A good steady output is always essential to ensure no unwanted restarts. If changing is on your mind at least try to obtain a gold rated power supply. Doesn't have to be a top end or overly high powered unit unless you are planing on a near future upgrade to a duel 6 or 8 pin powered GPU such as 980 upwards