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?
There are suggested room dimension ratios for minimum mode generation. Will the room be on a concrete slab? If so consider isolating the slab from the rest of the house. I have heard people even isolating the component area and the speakers from the rest of the room. If there is a Wife factor then consider having conduit placed in the floor before you pour your slab for speaker wire or component interconnects. Is this room going to be used for Home Theater too in the future? There is also the question of power. Run the lighting on a separate breaker, dedicated 20 Amp line for each amp, etc, etc. If you are going to have Home Theater then make sure you power running to the places you need it and plenty of it. (For Example, in the ceiling if you are using a projector or to the rear speakers if you go with powered speakers like Meridian or if you amps are in the back) A book I found very useful in the general principals of acoustics is "The Master Handbook of Acoustics." Several people have also recommended (but I have not read) "Sound Studio Construction on a Budget" both by F. Alton Everest. These books should answer most of your questions and instill many new ones. :-) Cheers and Good luck.
see August Stereophile "Fine Tunes" P.154 by Jonathan Scull. George Cardas' ideas for reducing "slap echo" via asymmetrical wall dimensions; even tunable rooms with a tapered-angle sidewall on rollers (if you're actually building a room, might as well go all-out). Good article.
Reference George Cardas' website, Cardas Audio Insights. Very helpful.
Positive Feedback is working on a series of articles about Winston Ma's listening room. I think somewhere around $300K was spent. It may share some ideas that can be utilized for much less. And, what is this stuff about walls on rollers? I hope that it is stable ...
Over at my dealers' he has these sort of CD rack looking things on the celing,right and left walls,No tube traps/or such. Sort of octagonal shapped wall behind the speakers./ no corners Any one been to Brooks Berdan's place?(So. Cal) Now to ans. the question Best room? mine/it's closer.Recres,the stable wall should be outside. Yes I'm keeping the day job.
I'm a building contractor. Of course the stable wall is on the outside. My concerns regard the ability of the "Wall on rollers" to not make noise or shake , rattle and roll during passages with extreme low frequencies. Ever hear one of those kids with 4 15 inch subwoofers in their car at the stoplight? That's where my concerns lie.
Tough area.....where do you begin, Dollars or(good) sense? I'm currently fighting with myself over the same dilemma. At this time I'm considering a round room, with a diameter of about 32 feet and 12 feet high...with two (2) interior walls, one (1) at each end; to be used as a home theater and sound room. I'm a architect, and have been fortunate enough to have built a couple of great sounding rooms, but this is a new wild hair.... catalogwiz
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.