Unless there is something physically wrong with it, this power supply is providing plenty of wattage for your system. I am more inclined to think that there is something wrong with the board itself. Did you buy this used?
Well, "Some" should keep their opinions to themselves; they really don't know what they are talking about.
If you really, really want to determine the requirements of your system, there are a number of power supply wattage calculators available on the web. Just do a search for "power supply calculator". I like the one provided by CoolerMaster; give it a try.
I think that you will find that you can run with as little as 450W, though the requirements of your graphics card(s) and the configuration of the rails inside the power supply itself may push the requirements to a higher level...
Hope this helps,
Great information from Scott, thanks for that information.
@mikylachosky, you may need to check power supply considerations available here:
Please check attachment: