Seeking horn array loudspeakers with a maximum price of $17,500.00 per pair.

sounds rich, full bodied and dynamic at 50-55 decibel levels

I question if that is possible with any loudspeaker.

Another recommendation for Volti Rivals. I really enjoy mine. Not even sure that you will have to turn on your big Bryston amp to get to 60 db…. You might need 1/10 of a watt on peaks w/ them at 98+ db sensitivity. Seriously, some amps don’t sound their best until significant power is drawn from them so you may consider a lower powered amp & maybe tubes.

Happy Khorn owner here. Ecstatic owner when subs were added. Easy to find latest iteration new/demo/used. With subs I was all in for under your budget.

Be that as it may I would think the Volti Rivals (with or with out subs) would thrill.

The big honking amp might be not quite the right fit????

used Avantgardes

https://www.hifishark.com/search?q=avantgarde

Why d you feel you need horns ? They don’t do anything  in imaging or detail better then a good Loudspeaker,  if you want a open baffle or dipole Qualio 

make 2 very good ones. And Spatial Audio make horn- open baffle  speakers.