Now I'm thinking about just adding a seperate power supply for the external radiator stand. Right now I have a 4-pin Molex extension cable running from my computer to the radiator stand. If I expand this thing the way I am thinking, it very well might end up over taxing my 1000 watt PSU if I add a 3rd GTX 580 card later on.
So, if my calculations are correct, I need at least 4.882A at 12VDC (58.584 watts) to power 2 MCP655 pumps and 18 Gentle Typhoon AP-14 fans.
For either $19.74 or $27.76, I can get an AC to 12VDC power supply (I've used them at work for various products) that is either 72 watts or 102 watts respectively.Meanwell RS-75-12 72 Watt @ 12VDCMeanwell RS-100-12 102 Watt @ 12VDC
They are relatively small, either 5.1" (or 6.3") by 3.9" by 1.5". I just have to find a spot to hide it. Most likely were the 6-channel fan controller is right now, as this would take it's place (aside from displaying FAN RPM, which will be fixed at 1450, and water temperature). Maybe I can find a simple multi-channel thermocoupler display somewhere.
Actually, I think I might go this route.
12VDC at 8A. External (don't have to worry about water leaking into the open power supply), and all I have to do is mount an on off switch and a bulkhead 5.5mm ID connector to the radiator stand. Best of all, it's only $18 shipped.