It seems like you already have an idea on ceiling mounting the speakers. You may also want to consider whether the room is enclosed or open. For an open area, direct radiating speakers may be preferable over dipoles and you may wish to have speakers similar to your front Martin Logans. Magnepans makes a line which installs on the walls with a bracket and which can be folded out of the way when not in use. On the other hand, for an enclosed room, consider dipoles such as the Paradigm ADP. I believe they come in white and can be fairly unobtrusive.
Sohail
