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

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.

Coherant loud speakers model 18.

I have Volti Rivals. Their treble is not grainy and their bass extension is superb in my room. I drive them with Quicksilver MidMono’s (EL34) and ToolShed 300Bs (WE).  Highly recommended!