> Nearly every PSU operates most efficiently somewhere in the middle of it's power range, operating a high power PSU at 20% capacity will use notably more power than a correctly sized one.

One note from a physics major who's first job out of college was a the electrical officer on a frigate: this applies to all electrical devices. This sort of "over-supply solves all problems" attitude is quaint when it's a home server. It really sucks when under-loaded 1MW diesel generators shit the bed almost weekly on deployment in the summer. Any idea how much hot-dark-and-quiet sucks when you're bobbing like a cork in the middle of the ocean in the summer? Now imagine you're the person that 250 hot, cranky people expect to fix it. Why? because some "contracting expert" in the Pentagon decided to "over-spec" the generators 25 years ago.