The stickers on PSUs mean nothing. The PSU makers can put whatever they want on the side of a PSU. Better indicators of quality are brand name, weight, and price. PowMax is known to make not-so-great quality products, one of the reviews on Newegg said this PSU is very light, and it's way underpriced compared to most 500+ watt PSUs from known, trusted brand names. I highly suspect a 300 watt Fortron would do much better than this PSU.
Powmax, Robanton, and Raidmax are all made by the same company, Leadman, and Powmax and Robanton seem to be their cheaper brands. This is what one of their best quality 400W PSUs looks like:
Tom's found that the 500W version couldn't put out more than 426W. In comparison, a 350W Fortron/Sparkle managed 454W.
And this is a 400W Powmax:
It's not simply the first PSU with smaller heatsinks and capacitors but a completely different design.
That 580W Powmax Demon looks bad because the "CE" on its sticker doesn't look like an official CE certification symbol, and the FCC and UL certifications don't have registration numbers listed with them.
If it looks to good to be true it probably is. In this case I know for a fact it is I know someone who has one. The power supply does not even come close to it's much touted 580W capacity. The 12V rail is hugely overrated in real terms if you have 5 fans 2 hard drives and a CD-ROM you have just about exceeded the capacity of the 12V rail. How do I know this because I seen my friend add a removeable Hard Drive Bay after he turned it on the 12V rail dropped to 11.5. That was when I told him I had seen enough and for him to get in the car and go buy himself a real power supply.