After years of replacing burned out PSU's, I've finally settled on just one brand. ANTEC Earthwatts nnn
I have one main system and one backup system and both are currently running Antec Earthwatts 750's
On most PSU's, (read the label carefully) the posted power rating is the Maximum One-Time Surge wattage.
That's the power that the PSU can supply for the first second or two after it's turned on, to charge the mobo cap's and start the fans and drive motors. Then de-rate that number by 20% to 30%, for the all day running wattage.
Shop carefully and don't get ripped off by a cheap PSU! Eh?
Many retail stores like "Staples" now sell only Antec power supplies.
Cheers mate!