For me, mid horn design and construction material extremely critical, Tractrix design and wood construction. Exponential metal or plastic horns cannot provide natural dispersion or timbre. Tweeter and mid drivers need to be in proper physical alignment for speaker time alignment, improves mid and high frequency balance .I have both mid and tweeter horns on separate baffles for optimum toe in or out, major improvement for sound staging, imaging. Improved crossover parts also improve timbre, sound stage and imaging.
Stock Klipsch Heritage greatest inherent quality is incredible micro dynamic expression, sense of live performers in room intoxicating. Resolution and transparency wonderful as well.
I understand some of my mods would not be easily applicable to a consumer market loudspeaker. Still, I'd like to see a Heritage state of art model; an ultimate expression of the basic design. As Don stated above, a speaker that does all the things stock Heritage does, only does it better. There really is no contest, modded Heritage is my final loudspeaker. I don't say this lightly, have never called any piece of audio equipment my end game, this is the single exception in over twenty five years as audiophile.
I'm not saying stock Klipsch Heritage is not a fine speaker, I understand the enthusiasm. Matched with sympathetic partnering equipment, inherent limitations can be minimized. I use mine with 845 SET, 300B monoblock SET and EL34 push pull, all wonderful, I'd next like to try 2A3. I'll also reiterate I've not heard latest Heritage, I'd hope they've improved since earlier models.