Im not mining with CPUs... I have them running at stock. I have thought about downclocking them or undervolting them to save juice. They have very little load ever placed on them and I dont think I would notice if they run slow. I've never done that before though. I have only overclocked for gaming with no regard for electrical use. But Ill give it a shot sometime when I'm bored. See how many watts I can save.
The room is 'outdoor' in that you have to go outside to get to it. But its insulated, the landlord calls it the 'shop'. My dog likes to sleep in there, the heat used to be nice. Summer barely lasts 3 months here, but I put an a/c in anyway.
undervolting your CPUs will only save you a few watts, maybe 10 combined across all systems? Your CPU will run almost completely idle (unless you set the intensity too high - 100% cpu bug) while mining.
5830s can be undervolted to only draw like 100-110 watts a piece IIRC (while still staying over 300MH/s), which should put your 7 card rig somewhere closer to 800-900 watts with the same MH/s.
Either way, nice setup!