The RASURBO REAL&Power series targets the budget oriented users that need an affordable PSU to power a low/middle end system. At least in Europe it's not easy to find a semi-modular PSU at 60 Euros, so RAPM550 earns a point here. Also the fact that it managed to operate at full power even at 50°C pleased me. However the loose voltage regulation at +12V and the sudden drop in performance over 440 W troubled me. In Crossload test 2 the +12V rail clearly showed that it can not handle the power that the manufacturer claims. On top of that Advanced Transient Response tests proved to be a Waterloo for RAPM550 since its minor rails performed bad. Thankfully the most significant rail, +12V, handled the transient loads well. In ripple/suppression measurements the situation reverses and +12V exhibits mediocre performance, here the minor rails have better DC quality.

In my humble opinion RAPM550 should be characterized as a 450W unit, not because it can't deliver 550W of power, but because it performs quite well up to this mark. If your needs are covered with about 450W and you are on a tight budget then RAPM550 is a decent choice but if you expect to regularly draw well beyond 450 W of power, then you should look elsewhere.