If we are talking about full range horns, then any "Top Horn Speaker" made today would have to have a bass horn to handle the bass below 100Hz, preferably a forward firing one, and one that goes down to at least 30Hz @ -3dB, or 20Hz @ -3dB would be even better. One would have to consider a Cessaro horn as they will custom make you a horn system including a bass horn to fit in and match your room, plus they use the very best drivers, parts and materials.
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Having said the above, a really clever design would be a Horn speaker that gives 80% to 90% of the top models but at a really affordable price. For that I would give the prize to the Klipsch Cornwall IV, but in the context of this thread the Cornwall IV can be ruled out...