My $0.02: If I were going to build a dedicated listening room, I would hire a professional who does that for a living. There are so many companies that build studios, and I've seen them mention they also do personal listening rooms. I know Michael Green does this. Good luck.
Best Listening Room?
I am considering building an addition to my house, and figured I'd build a dedicated listening room while I am at it. So the question is, what is the best listening room one can reasonably build? Should it be square/rectangular or have tapered walls? Round corners? Should the ceiling/roof be high or low? Flat or angled? What is the best floor, wall and ceiling covering material? Etc etc... In other words: If you were to start from scratch, what would be the best room you could build?