Keen to build a quiet, power-efficient always-on HTPC/media server, I've been looking at mini ITX boards that have their own external power-brick style power supply. These appeal because they are silent, do not contribute to heat in the case and (although I've seen mixed information about this) should be more power-efficient at low wattages like 25W.
However, I've read multiple reports about both this ASUS board and this Zotac board that the power brick included with them is extremely inefficient, using around 20W just by itself (with nothing plugged in) and increasing the overall power usage by 20W, so instead of the 25W draw expected from these devices, it's 45W. Everything, apparently, still works fine. That's incredibly poor power efficiency and I'd do better with an internal 300W seasonic or something.
Are these power bricks just unreliable in general? Why do multiple people (including some reviews) seem to have "bad" ones, even from totally different manufacturers? Should I be avoiding them for an always-on media server/HTPC? I'm not too concerned about the power usage, more that I don't want something to get unnecessarily hot just for no good reason other than a fault.