Intel Q6600 Core 2 Quad @ 2.8gHz
Asus P5K Deluxe Wifi
Zotec geForce 8600GTS
OCZ Reaper PC2-6400 2 gig kit
Kingwin Heatpipe Direct Touch CPU Cooler
Zalman VF-1000LED GPU Cooler
Sunbeamtech Tuniq mid-tower case
Zalman ZM-MFC2 Fan Controller
2 x Hitachi SATA hard drives
Unfortunately, I don't have a pair of 8800GTXs in SLI for testing the Rosewill RS850-S-B, but I do have an interesting tool in the Zalman ZM-MFC2 Fan Controller, a meter that actually tells how many watts my rig is drawing. So, rather than just measure voltage, and measure it again with things maxed out, I will be able to tell how much power that my system is consuming.
Keep in mind that watts drawn is not the same as watts produced by the PSU; that takes some pretty sophisticated testing equipment. I'm just trying to illustrate how much harder the PSU is being forced to work.
With a little experimentation, I find that my rig at idle draws 134 watts, and with both HDDs running, optical drive running, fans, CPU, and GPU maxxed, it draws 205 watts. That's a 53% increase. The PSU at idle produced 12.33vdc, and 5.01vdc. At full load, it dropped to 12.23vdc, and remained at 5.01vdc.
I consider dropping only a tenth of a volt negligible, especially since the voltage is still well over 12v. Again, the testing doesn't prove what a pair of video cards in SLI would, but I'm satisfied that the RS850-S-B could handle the real thing.