If the PSU for the Quadfather includes components for 3.3V, 5V, and 12V rails. It can't put out all 1000 W towards any one line or voltage level. Also, there is the energy efficiency to contend with; (power out) = (power in) - (heat and other energy drains). So if it's using 860 W at the wall (or is it 760 W? Your inclusion / exclusion of the monitor made measurements unnecessarily confusing), then it's probably using a max of 0.85 * 860 or 730 W internally. That 730 W implies a hefty margin of safety compared to the 1 kW rating. But you have to consider that there are limits on individual rails so that supply may have been necessitated by the dual CPUs, or the dual 8800 GTXs, even though the supplies for 3.3 V and 5V have plenty of room to spare.
So: the individual line output requirements inside the Qfather need to be considered when evaluating the choice of PSU, and margin of safety/error. I don't think your article talks about that enough.
Also, the PS3 will likely have similar limits on individual lines, but its power supply was likely pieced together from parts of commercial PSU components, according to the needs of the HW. Given that, I would expect it to use a smaller PSU than the rated 380 W (which represents ~450 W at the wall) - as you demonstrated in your article. The PSU is far larger than necessary, which means that the PSU is wasting more power than it needs to at all times, and particularly at idle. That's what tells me that the PSU for the PS3 isn't very energy-conscious. Not the fact that it uses less power than a Qfather.