New PSU with "550 watts", only 2 SATA, ridiculously low 12v current, ridiculously high 3.3v and 5v, and only passive PFC?
I can guarantee you absolutely 100% that's a piece of garbage.
And while older PCs will prefer 3.3v and 5v over 12v, a modern PC PSU built like that ALWAYS signifies low quality. No exceptions. It's possible to build a quality supply with mostly 5v and 3.3v, but there are no PCs out there for which that would make a useful product (no older PC needs a 550w supply and any newer PC needing 550w needs it mostly in the +12v rail). And so nobody makes a quality supply like that anymore. It's all garbage. (Edit to note: PSUs that have even more total power, have tons of 12v, and also have lots of 5v and 3.3v current are fine if they are from a decent brand. But if it's a newer supply, has the 5v and 3.3v current, but lacks a big 12v rail, it's crap. The large FSP supply mentioned a few posts above should be fine as FSP is a pretty good brand and that supply has plenty of 12v current available too. Though if you use such a large PSU in an old rig that doesn't need it, you may encounter cross-loading issues stemming from not enough load on the 12v rail.)
I wouldn't pay even £20 for a supply like that (Edit to clarify: well I'm in the US so it'd be $ for me... but I honestly think a PSU like that is only worth $20-30 new at retail; I'm not trolling with that number. And I still wouldn't recommend ANYONE buy a supply like that at $20). I literally wouldn't use it even if somebody gave it to me for free.
It does have the UL logo which is a good sign, but I'd say it's likely counterfeit. And even then, UL certification only indicates a possible decent product; it's not a definite.
I could buy some really good PSUs at that pricepoint. But for retro stuff save yourself some cash and by a used Enermax Noisetaker (the ATX12v 1.3 series) or a PC Power & Cooling Turbo Cool 350w, 425w or 510w. (No need for 510w, but hey it'll be a quality supply and you can get them pretty cheap sometimes used.)
By the way, when looking at PSUs, do not just look at the currents for each rail. ATX power supplies also have a power rating for the 3.3v and 5v rails combined... It can be as low as ~80 watts, or it can be over 200 watts. Very important spec and I have yet to see anyone else mention it. A power supply can offer lots of current on 3.3v or 5v, but not (always) on both at the same time because of this rating that everyone seems to ignore. Not good! Lots of recent FSP (Fortron/Sparkle) models have ~130w which will be fine for many fairly standard retro rigs but some of the smaller ones and some other brands have 80w which should be avoided in most cases.
Retro hardware can be expensive at times, and power supplies are the one component that tend to take other stuff out with them if they fail. They are also the one component that is relatively likely to start a fire if it fails, particularly low quality units. Brands like Allied/Deer were known for literally starting fires. I owned an Allied PSU once... it was "AMD certified" but when I found out that such certification was useless and the supply was downright dangerous, I changed my ways. Probably a very similar PSU to what this is, too.
Edit: By the way, FSP is actually one of the better manufacturers. I'd probably take Enhance, Enermax, Flextronics, Seasonic or Super Flower over FSP, but I'd still be happy with an FSP over just about anything else. (Edit to note: I said PC Power & Cooling above which is now owned by OCZ, and is a still decent product, the ones I mentioned above are pre-OCZ when the brand was considered by many to be the absolute best.)
Yes, I always ramble this much.
