Building a Music Room

I am toying with the idea of adding a music room on to my house. It will be for 2 channel only SET amp power and 110db efficent horns without any subs. With the speakers in the conners what are considered to be the best dimensions for such a room? Any advice or ideas will be appreciated!!!
Jsman...if you are going to go through expense of building an add-on room for 2-ch audio, I would involve a professional acoustician or an outfit like Rives Audio from the start, not only for room dimensions but also for advise on materials to use in the construction for proper isolation, soundproofing, quiet HVAC design, electrical wiring, etc...The upfront investment ought to pay dividends in spades.
A project like yours was the subject of an article in HiFi+. Try checking out issues from Jan-March('09).
I agree with Cmalak. If I had the money to build a dedicated or semi-dedicated music room, Rives would absolutely be my first stop. The Level One price is not bad when considered in the total price of building a new room. Of course it can get as expensive as you want it to - just like the rest of this hobby. :)

In my opinion, there is no better investment you can make than the room. When I constructed my listening rooms, I relied heavily on F. Alton Everest's book, "Master Handbook of Acoustics". A good starting point is getting the proportions (rather than dimensions) of the room right. There's useful information in this book and others now avaialable. If, on the other hand, you're looking to contract the job out, Rives is a good starting point. Here's a link to some literature: Best of luck.
Now may be the ideal time, assuming you plan to stay in your house for at least five years, as the building trades are slow, so you could most likely get a great price. Consider making it a 'media' room to increase the WAF. I built a media room in a new house many years ago, but it was in the basement. Would not do that again. Go for above grade, on a slab, carpeted. Don't design the room around connor speakers. I had K-horns and found that you get tired of the sound, quickly. Do consider Rives for the design phase, no one does it better. Hey, the government will give you a nice tax credit with all the insulation and special windows you will need to put in.
Ok guys thanks for the replys so far!!!
buconero my speakers are extremly modded 2"wooden tractrix horns/2"BMS drivers and a xover designed for them. The bass bins are the only unchanged area of my speakers. I doubt that I will grow tired of what I am hearing now, thanks just the same for the tip. I only mention the conner horns as a refrence to get info on the size of the room I should be looking into.
If you build on a slab, design an area to run your cables. Put the speakers and amps on one end and front end down by you so plan on running a long interconnect. Cover the slab with 2x4s layed flat, then wood across the 2x4s with carpet on top of the wood. A wood floor sounds better than a concrete slab with carpet. For carpet, consider a wool type instead of synthetic. Rives is good, but there are others. See if there is a Negwer materials store near you. They have acoustic consultants.