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

I recommend the Fleetwood Deville SQ, adding just a little more $ or if you can find a used pair for sale. They are wonderful sounding,very detailed ( even in low volume ) great bass and the horn tweeter , just right and not too horn sounding but extremely detailed especially the voices.Check them out on YouTube, one of Steve Hoffman’s favourite speakers.

Look at Joseph Crowe Audio. 

Most of my listening is at those volume levels and the sound is rich and full.

my amps are 4.5 watt monoblocks type 45 tubes.

Another Volti recommendation. But if I were you, I'd be looking at high quality SET amps to replace that Brightson......

 You have some great choices at your price point, especially if you consider used.

Agree with ozzy62, I would not want your amp with horns.

Agree with @vicdior . The Fleetwood Deville. Did an audition recently. They are difficult to beat at that price point. Definitely something to go listen to. Some don't like their look however. Best of luck and keep us posted.