Here's another, older system I have here: 2.4GHz P4, 2GB DDR SDRAM, Intel mobo, Radeon 7000/VE PCI graphics card, one firewire card, a lone older 160GB IDE hard disk, two optical drives, and a floppy drive, ps2 mouse + keyboard.

Full off (back panel PSU switch), it draws 0.017 amps, ~2W.
Turned "off", it draws .05 amps @ 120V, roughly 6W.
Steady idle-state gives 0.55 amps @ 120V, roughly 66W.
Full load(*) gives 0.94 amps @ 120V, roughly 113W.

(*) CPU 100% busy, hard disk 100% busy, mouse moving windows rapidly around the screen.

Mmm.. I don't like the fact that this (Enermax) PSU doesn't *really* turn everything off when the back button is off.. maybe time to rewire it.

Cheers