Soldato
I have an XFX Pro 750W Bronze which is about 7 1/2 years old.
I've got a 650w gold rated Silverstone PSU that was powering off when drawing about 500 from the wall. Do PSUs tend to fail to deliver rated wattage when they're on the way out?
They get less efficient over time as components degrade, but it's difficult to compare what it's pulling from the wall, a PC PSU is basically an AC/DC converter so you'll always have an efficiency loss in the conversion.
That said, if a 650 is pulling 500w from the mains, it's got to have a pretty heavy load on it