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

Thinking along the lines of Snook2, I would seriously consider getting a full range speakers and adding 2 powered subs (for example JL113). This will be more cost effective than a speaker with large woofers, gives you far more options, more placement flexibility and you can typically EQ the subs (eihter build in or separete sub EQ box.

You will need a very large horn loudspeaker or line array to fill such a space. Maybe consider used or custom built in your price range.

Alex2, Anat3 Sig @10-20k?? (even used?)

I think by this time we are seeing what some of the issues are with filling a large room. Nearly everyone who mentions a speaker with lower efficiencies is also recommending a subwoofer and quite often some very powerful amplifiers.

The problem with this is always blend, and system complexity rarely contributes to musicality.

This is why I recommended the Classic Audio Loudspeaker. Fist off, you won't need a sub. The T3 has dual 15" woofers, one down-firing and the other forward firing. With 98 db efficiency, you will be able to operate a tube amp with only 60 watts and do nicely filling the space.

The problem here is that you can count the number of 500+ watt amps on one hand (with fingers left over) that sound like anything close to real music!

So if you have a speaker of higher efficiency you have a much wider range of amplifiers available!

A few years ago we set up a system at RMAF, in the biggest room (A ballroom) available at the show. I think the room was a good 120 feet long, and at least 60 feet wide. We had no trouble filling it with power to spare using a set of Classic Audio Loudspeakers and a set of Atma-Sphere MA-1s. For the most part the amps were loafing. That is how you want the system to work. If you are pushing it hard all the time there is no way its also going to be sounding its best.

+1 Atmasphere..

Exact same reasons I named big Tannoys.

Avoiding complication to system, and staying within stated budget (used).