What about tile? Any soft surface, like floating wood flooring cannot be improved upon or "tuned" once installed. Yes, tile is hard, but is a good, solid, surface that can be "tuned" with area rugs to your liking. Nothing wrong with the raw stained concrete though for the same reason. You are on the right track with doubling up the sheet rock. You want a solid non spongy wall, and the floor is no different. I'd rather start with a solid, hard room that I could tune than with something already spongy.
Audio room floor question
I know this question has come up before but please indulge me. I'm adding on and am building a room that will serve as my HiFi room. I'm not going the "professional" route but I do want to make the room as HiFi friendly as possible. The dimensions are set so I can't do anything about that. I have a heavy concrete floor poured. What is the best floor covering? I could use hardwood glued, floating hardwood, linoleum, or I could just leave it concrete and add area rugs and pads. I don't want to use carpet as there will be a hallway and an outside door that will bring in snow and mud. Thanks