I've had my PSU for about a year now and I know it's not one of the "more-known" brands but I've never had any problems at all with it
CiT 500w (2 +12V rails combined to 27A).
Hardware Monitor never reports less than 11.58v or more than 11.78v on the +12V rail(s), other rails are almost always at what they say they are.
I'm not too knowledgeable with how power supplies work, just the basics.
When I do my setup in the eXtreme PSU Wattage calculator, it says I need 270w. I divide this by 12 and get 22.5A, this being the amperage requirement for the computer. When I divide 270 by 11.58 (lowest voltage at +12Vs), I get 23.3A. Now I know that PSUs do wear down over time, but is it close to the point where I should get a new one?