Large Room which speakers?

I am in a reverse situation having the large pair of speakers but not the room.
JBL 4676-A (two-way system) Using the JBL 4550 BKA bottom cabinets.

I would recommend you read my review on the Lawrence Audio Double Bass Speaker on hometheaterreview.com for the details why this is a great speaker and might be exactly what you are looking for for your large acoustic space. I don't know if it would fit into your budget, however it would sound wonderful in your room.

How far you sit from the speakers is as important as room size. Also depends on what your idea of "fill the room" is. I would suppose the Hornings do have enough gas in the tank to satisfy most in a room that size, but still would have their limits.

I don't have a room that large, but if I did ...

I would go big on the speakers, based on the information you provided:

Big Duntechs, Magneplanar 1-D, Sound Labs, Genesis, Quintessence, Wilson, Pipedreams, etc.

A lot will depend on your listening position. If you sit reasonably close to the speakers, your choices are plentiful. If you're twenty feet back, that's a different kettle of fish and you'll probably want something a little bottom heavy. If you're moving around and the listening position is unpredictable, then wide dispersion might be beneficial. Therefore, you might want to think twice about narrow dispersion, horn loaded designs like (I believe) the Hornings. Further, if you really want to energize that entire space, you'll need to consider the speaker's max SPL capability.

In your shoes, I might think hard about the big MBLs, if you can swing a pair and the required amplification.