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

We're listening. Now, show me a C.A.R. T1 for 10 - 20 K.

Consider the Von Schweikert VR-44s or vr 35s.

You could look used and get a pair of VR-5s.

All of the above are simply stunning speakers.

A little known speaker that would fill the room with great sound is the old Pro Ac Studio towers circa 1988. They were 5k new back then and you can probably get a good deal if you find a pair. The are efficient, play loud without distortion and need a large room to sound their best.

'It is THE luxury of high end audio to listen at high volumes without stress'. That's it in a nutshell and is why efficiency is indicated in this situation'

This is exactly the experience I have had with the GR Research Super V.
I was shocked that I could talk to a friend next to me and we could clearly understand each other though the volume was at about 90-95 dB.

And the Servo Bass is the best you will hear anywhere.

I'd consider powered studio monitors like those from Genelec and Equator Audio. No audiophile speaker can match bi or tri amped professional monitors for accuracy at high volumes -
Equator Audio Q15 -
Description: Powered 15” 2-way Reference Monitor
Frequency Response (+/- 3dB): 29Hz - 22 kHz
Recommended Line Level Input: 10mV-2V
Amplifier Power (LF/HF): 1000W/200W
Amplifier Peak Power (LF/HF): 2000W/400W
Sensitivity: 1w/1m output, 94dB
Max SPL (per pair): =117dB
Genelec
The Genelec 1039A is a very powerful monitor system, designed for large control rooms. It consists of a 320 litres speaker enclosure and a 7U 19" equipment rack which contains active crossovers, three channel power amplifiers and driver protection circuitry.

The speakers are designed for flush mounting in the control room wall, although they may be used free standing and can produce peak sound pressure levels in excess of 126 dB.

Audiophile speakers melt at these volume levels, as do the amps you need for them.