Aye, and they were brand new - which raises the point that it's not good to be at either side of the bathtub curve, eh? Perhaps buying a one-year-old PSU second-hand is the optimal solution, providing the warranty is transferable! According to Wikipedia's summary of the 80 PLUS standard, required efficiency for a 230V non-redundant power supply in order to get certification varies from 82% at 20% load, 85% at 50% load, and 82% at 100% load for non-metallic 80 PLUS up to 90% at 10% load, 94% at 20% load, 96% at 50% load, and 94% at 100% load. In other words, you want to be running your PSU at 50%-ish for whatever you use it for most. If you only turn your PC on to game and it draws 400W when doing so then you're going to want an 800W PSU; if you leave your PC running at idle and it's drawing 30W, you're going to want a much smaller PSU that can still handle peak loads (so, if it's 400W while gaming and 30W while idle, a 450W-or-better PSU). The idea being to spend the bulk of your time as close to peak efficiency as possible. Realistically speaking, though, we're talking a two-to-three percentage point difference in efficiency at different loads, so at the end of the day buy what you want!