I think dual socket systems are more efficient using one PSU instead of two separate systems. Didn't skimp on the PSU, gold rated. Better to pay up front for quality parts than pay for it later.

"What type of plug-in gizzmo in the $10 range is used to measure power usage? I'm very interested in using something like that to check power use.

And where would I find such a device"

Eb*y in my case.

Mine was shipped from Hong-Kong to the Uk. The first one I ordered didn't show up. The second did. True cost= $20.00 :-)

Accuracy? Who knows?

Let me add another. This is an i3-2100 CPU @ 3.10GHz - 2 cores plus hyper-threading, 2 gigs ram, and Ubuntu 11.04. 1 wifi card and 1 x 250g drive. No monitor:

83-89 watts.

Maybe it's the drive which causes the fluctuations?

With an Nvidia 8400GS GPU card in there the consumption went up to 105 watts. I pulled it out, WGC don't use no GPU, right?

I shifted all my crunching to the i3, and it runs at 100 per cent. It has the great advantage of running cool, and using less juice, though less points.