Wide dispersion + high efficiency + detail + coherence in a speaker?

Ever thought of a pr
of belles?

I run mine thru a 6900 mac they'll make your ears bleed a d with total clarity

@charles1dad   thanks for your recommendation.  
i wonder anyone have experience with Vaughn Loudspeakers. very interesting crossover network but didn't spec the crossover point! 
-p

A budget has not been mentioned.
One speaker that has solved similar desires I have in a speaker is the Classic Audio Loudspeaker. I have the model T-3.3.

It is 98 db, 16 ohms, goes from 20Hz to 35KHz. The all important midrange is a beryllium diaphragm compression driver that is field coil powered. The field coils insure that the speaker is very fast since unlike permanent magnets, when you put amplifier current in the voice coil the magnetic field does not sag in turn. This speeds up the driver; on top of that the beryllium construction (with a Kapton surround) means that the first breakup is at about 35KHz, so not only is the speaker fast but its smooth, very much like an ESL, but with considerably greater overall efficiency. The crossovers are 6db with Mundorf capacitors. The Kapton surround allows the compression driver to go down lower than its horn does, so its very free of artifacts and the drivers blend effortlessly- it is very cohesive.

As far as dispersion goes, that is the weak point, but its really only the higher frequencies- the speaker images easily and the sweet spot is wide if you are back more than 8 feet. I have my speakers about six inches from the wall behind them and they image quite well, so despite their size they are easy to set up in most rooms. I can play the system softly and hear every note, if I play higher volumes its so effortless I can't tell how loud its playing unless I try to talk to someone sitting next to me.

In a nutshell this speaker is one of the most uncolored, revealing speakers I've heard; its really easy to drive and no need for a sub- it goes down lower than a a lot of subs do (dual 15" woofers in each cabinet).

atmosphere,
That sounds like a heck of a speaker.  I've only heard one or two of the Classic Audio speakers at shows and enjoyed what I heard.   If I had the space I would definitely have tried out horn speakers by now, but they just don't fit at all in my scenario.
(Btw, something fascinating to me is how, as counterintuitive as it may be, there is something of the character of various speakers that actually seems to come through on the many youtube demo videos.  Sometimes it seems like the character of a lowther horn speaker really comes through, a sense of liveliness, dynamics, or just the more "full" and chunky sound seems to be present vs recordings of other speakers  (sometimes you can even hear the horn honk coloration on voices...I know some horns don't have this...).