Big, big room -- which 10-20k speakers?

a pair of altec nineteens would perform wonderfully in that large open space

a pair of altec nineteens would perform wonderfully in that large open space

While I in no way consider myself in the same class of expertise as some of the respondents, I would suggest a look at Legacy Audio. Legacy is not as exotic as most of the suggestions here; But I heard the newest version of the Whispers at CES 2 years ago. The only speaker I liked better was the Anat Studio II, which is exponentially more expensive. I have a similar size room. I use two Legacy Focus and the sound really is unbelievable. I have a bit more power available in my amp which may help; But the New Whispers come with built in dual 500 watt Amps powering four 15 inch drivers each side. The extra power and piston area will surely go along way toward filling a large room. They are also very efficient. Have fun designing!
http://www.legacyaudio.com/products/view/whisper-xd/

There are so many choices to make, but only you know the kind of sound you are looking for. My room is essentially 20 X 30 X 25 high. My main speakers Coincident Pure Reference I bought used, two years old. My mono amps are PassLabs XA100.5's. They each drive 100 watts in pure class 'A' sound. Coincident speakers can be driven by as little as 25 watts or 500 watts, your choice. Right now I can drive well over 106 SPL at 10 feet. In my own humble opinion it is more about the sound you want and enjoy than an absolute number of power watts. All speakers are different at different levels of sound. Take time! By the way I also have two SVS Ultra13 subs that are blended in and helps create my own masterpiece. I had a friend down from Michigan to spend a few hours listening. He was astounded! And I had sold him previously, my Legacy Focus, which he loves.
Coincident speakers are built to hold an average 6 to 8 ohms across the frequency band to make selecting a power amp easier. These large speakers, weigh over 200 pounds and are reasonably priced used at around 10K versus 22K new.
The other choice to consider would be the BE-20 at roughly the same price. The sound is a little fuller. Usher BE-20 is their top of the line.
Either way you can't go wrong.
Choices choices nothing but choices.
Good luck and happy hunting!
Rich

I am envious of your room dimensions, especially the ceilings. Way to go!
A sub/sat system might surprise you...utilizing two identical subs of good quality.
But for stereo, I recommend Legacy Signature II's or better. I have the Sig IIs and they are indeed full range speakers in my room. Although, being so large, I would consider a speaker more suited for my smallish, cube-like listening room. With treated walls, my Sig II's are almost too much. Sub-wise: in black, I would consider selling my pair of Sunfire Professionals. They were the largest of that line of Sunfire sub-woofers, driver-wise as well as "Carver watts" power output. [email protected] for any continued communication.
Whatever you do, take advantage of your wonderful listening area by purchasing speakers that are large enough to take FULL advantage of such a "space filled" area for acoustic reproduction. If you use subs, get them in exact matching pairs, and take home two. Do not let that glorious listening space be ignored.
Good luck and enjoy the search.

Truthfully Envious, tonehead