The Perfect Room?

I am building an addition on my house, and am considering (read, begging my wife) building a dedicated listening room in the basement. Of course, it will be perfect, because all of you will guide me in this project. I'm not asking about the equipment, I'm talking about the room itself. What is the 'perfect' size, dimensions, shape, building materials, etc for a 2 channel audio room. While I'm at it, I'd better consider a multi-channel room, even though I don't currently pan to do that. Any good articles on the subject?

THanks.

John