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

I like the suggestions of Volti speakers.  I also like some open baffle speakers that utilize horn midrange/tweeter arrays, like the PureAudioProject speakers, although I think the full range driver and coaxial and AMT midrange/tweeter modules that are options for their speakers are also very good alternatives to their horn option.  The recommendation for Charney Audio is also good, although they do not utilize a compression driver/horn array, and instead, employ a single full range driver in a quarter wave backloaded horn configuration.  Perhaps not a horn system, but, very much in the same family in terms of sound and shockingly good.  The full range driver/powered woofer speakers from Rethm are also in the same sonic camp.

If you can get to the Washington DC area, check out Deja Vu Audio.  They are a retail business, but, they also make a lot of their own speakers, amplifiers, linestages, phono stages and DACs.  They make extremely good horn-based systems for around $12k that utilize modern drivers, and even better systems utilizing vintage compression drivers and horns (but more expensive).  Whether you buy anything there or not, it will be a blast hearing their custom gear.  It is their belief that the amplifier is at least as important as the speaker, and I don't think they will sell someone a custom speaker unless it will be used with appropriate tube amplification (not all tube amplifiers fit that description).

If you end up choosing something that is high in efficiency, I think you should explore low-powered tube amplification as an alternative to your Bryston amplifiers.  Most solid state amps sound boring and lifeless compared to good low-powered tube amps, and the Bryston amps I've heard are not an exception.

@kjl1065 If you don't mind used see here. 

Mike

Used Avantgarde Acoustic horn speakers is another option.

Let’s not forget that most options mentioned from Klipsch and Volti I would classify as “hybrids”. Horn loaded mid and hi frequency drivers, ported dynamic woofers.

Gotta buy the Volti Vittora, Klipsch Klipschorn, LaScala or Heritage Jubilee for true 

horn loading from top to bottom.

The advantage of extremely efficient speakers is that it allows you to use SET amps. I've had Avantgarde Duos for a long time, not necessarily recommending them-- they require supplemental woofers and in my experience, a change in front end- but I've been using Lamm ML2s for a long time and those amps are musical as hell. I would suggest that you consider both the speaker and amplifier because the relationship is critical. I moved from some highly regarded cartridges-- Lyras and Airtights, and it was only changing to the Koetsu stone bodies that made a real difference-- particularly in the bass region. I now have fully dimensional bass, but added subwoofers and DSP'd them to get the lower regions to accomplish what the mid-high frequency spectrum was capable of.