Interesting Room Idea
Well, maybe you do not need an audition room, but the new facility of the National Opera Center can give you some new ideas on what an ideal listening room could take. A link to a discussion, and picture, of the room that appeared in the New York Times is:
One of the important features of the room is a curved ceiling of narrow wood slats. The room itself looks like a big k-Horn.
Since the room is mainly used for auditioning of the vocal instrument, it provides excellent acoustics. Most audiophiles will tell you that the reproduction of the human voice, especially female, is the most critical test for a great listening system.
Hopefully, many artists will be doing their recordings there.
Sadly, the Times article did not mention who the acoustic designer/architect of the spaces were. These people get too little credit for the important work they do.