building a room from the ground up...

I'm looking for listers experiences in building their dedicated listening rooms. We will be building down the road and I want to make sure I don't overlook anything easy to do during construction that will aid in great sound after completion. Room will be approx 14' x 20' w/ 9' ceiling. I am already planning separate AC feeds for the room divided into 4 clusters, each on its own dedicated breaker( cluster for Digital, Amps, other audio, and lights.) What I would love is some real world advice on construction technique to make the room extremely solid and relatively soundproof to the rest of the house. Right now, I've heard good things about spacing all support joists and studs closer together that required and varying the distance between them to get different size cavities behind the sheetrock. Double sheetrock has been suggested. Anything that works, I'm willing to experiment with. Bring on the crazy and the not so crazy ideas. Please try to stick to normally available materials (no kevlar walls, etc...). Additionally, I'd like to hear of experiences in how to design a good sounding (natural sounding)room. I've looked at live end dead end, no parrallel walls, etc., but solicit any opinion. Thanks for all responses.
Two books by F. Alton Everest should be required reading: (1) The Master Handbook of Acoustics, and (2) Sound Studio Construction on a Budget. In (1), Everest analyzes main room nodes for a room very close to yours in dimensions, and you can see how to do it for yours and maybe change things for the better. (2) is about 10 years newer than (1), and is a lot more up-to-date on RPG-style acoustic treatment. If you want DIY info on those devices, I make them out of Styrofoam and could email you theory-and-practice sheets.
If at all possible, you should attempt to prioritize (via high current, lowest resistance) the a/c power for your dedicated room by using a satellite a/c panel very close in proximity to your mains input in your house (unless that is where your normal breaker panel is located). Separate outlet ground runs connecting to a central fixed point at the new separate ground stake will aid to reduce a/c noise.
One easy one is (assuming raised pier foundation) using manufactured I-beam joists vs. 2x4's. Essentially cures any possible long-term floor squeak, but you probably already knew that one. Another trick used in our recording studios is to build metallic netting (even chicken wire or other cheap, conductive fence material) into floor, ceiling, and all four walls, make sure all surfaces are connected at some point via solder, then have your electrician ground the whole mess. Potential induced RF etc. goes away. Just a caveat, I'm not a contractor or an electrician, just a recording musician & mortgage guy who's worked for a lot of new home builders.
I built a house five years ago with a dedicated media room. I used five dedicated 20A circuits for power. All walls were double-thick drywall with insulation bats between the joists. Floor was double-thick plywood, covered by wood flooring. The key to making the room spectacular is that the ceiling slopes 6" from the farthermost point in the room from the speakers, and the walls are toed out 6". Therefore, there are no parallel surfaces, which eliminates any need for any kind of room tuning. With the exception of an approx. 3db bump at 40hz, the room is flat 20-20K. Sloping the ceiling and toeing out the walls are the keys.
I wondered if anyone has used cement board ('Wonderboard') instead of drywall. I'd expect it to allow less bass to escape without having to resort to full masonry. However, I haven't seen it in 4' x 8' sheets. Good luck, Jan
Tom Nice wrote: "Two books by F. Alton Everest should be required reading: (1) The Master Handbook of Acoustics, and (2) Sound Studio Construction on a Budget.". I bought No. 1 from Amazon; the book has a lot of information, but I thought it was poorly organized, examples before theory, but the examples refer to the theory. So, once I read the theory chapters, the examples started to make sense. The theory was OK, not super for sure; the focus is on studios, keep that in mind. There is a new edition of No. 2 that is supposed to come out later this month, I am waiting for it to be released before I buy it.