Du ma,
I think you can get de-humidifiers that do pretty much the exact opposite of humidifiers. I've never used one myself, but it might be worth looking into. In the long run, I have heard of people with very large tanks (500G +) having problems with mildew and rot in their ceilings and walls due to the evaporation. I don't know if this is something you really need to worry about though.
As for the tank situation, I have a small room in my basement that houses most of my tanks. It's pretty nice, in that it has a door to close it off from the rest of the area, and it's not too large, so it contains heat fairly well. In this room I have:
60G - housing the last of my angels until I sell them
60G - grow out for 6 juvenile discus
50G - quarantine from my latest plec run (a few royals + cardinal tetras)
50G - zeb tank (5 fry, 2 adults coming today

)
29G - hospital tank, currently w/ 2 discus that had a nematode outbreak
2 X 50G - RO storage, heated, aerated etc.
Then I have my displays:
90G - living room, planted south american. Will eventually house discus, but currently I only have a few corys, a german blue ram, a common plec, and 1 L066.
75G - Den. This tank houses my big royal (13") and my black ghost (7"). Also temporary home for my pair of angels, but I will be letting them go too.
Val