Another thing to consider...for a UTH to raise the ambient air temps of the tank you mentioned, in a room as cold as you mentioned, it will be running HOT. Obviously, how hot depends on the size of the UTH, but I think they will need to run hot enough to place any plant life in jeopardy. If this is a planted tank, I would probably rule out a UTH, especially, with 2-3 inches of bedding.

Bart