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.
