"The Ultra High-End Speaker."

If "ultra high end" is defined, even in part, by price, the Revel speakers do not qualify.  But, if it is performance, as measured by the owner satisfaction, it is entirely possible for that speaker, or one even less costly to qualify.  Even taking subjectivity out of the equation, there is no such thing as a best speaker that is superior in all aspects of performance, and not everyone agrees on which aspects have higher priority.  Add back subjectivity and there is nothing close to a consensus on ANY speaker being "good" sounding, never mind anything close to "best" sounding.  On top of this, there is no speaker that is appropriate to all rooms.  I personally find that low-powered tube amplifiers tend to be the best sounding amplifiers, and I have very specific favorite amps; that necessitates using certain types of speakers that then relegate others to less that ultra high end for my personal selection.

I've heard ultra expensive custom speakers that sound fantastic.  One such system was about 5 ft wide, by 4 feet deep by 8.5 feet tall.  It has twin 18" woofers, a giant horn midrange with field coil midrange compression drivers and a field coil tweeter.  Truly no expense was spared.  But, even it could not do everything, and the "compromises" might disqualify this speaker for another listener.  The woofers were quite restricted in output below about 35 hz.  Why? Because the requirement of ultra fast and nimble performance to match the midrange compression driver and the extended range for the shallow crossover at 400 hz or so, meant the driver had to be built with ultra low weight cones, and a surround that restricted the range of movement.  This meant compromising ultra deep response. 

In other respects, I suspect that great subjective performance in one area necessarily means affecting performance in another area; for example, the sense of midrange clarity might be a product, at least in part, of a leaner upper bass response because that bass tends to "muddy" the sound, but, if one also likes the warmer sound of a richer upper bass response, one cannot "optimize" both.  Hence, ultra high end might minimize compromises, but, it cannot eliminate them and the right balance could be found in a speaker that is cheaper, better suited to one's taste, and more appropriate for the particular room.

I have heard a number of rooms built from the ground up as audio rooms with full blown complete room treatment.  Even with such rooms, subjective impression of the rooms vary greatly.  Most of such rooms were, to me, disappointing—too dry and analytical sounding with bleached out harmonics.  
 

The best was a $250,000 room designed by an acoustic architect.  That room did not look like it was treated because most treatment was hidden behind the wall coverings, including the truly giant bass traps in all four corners.  The front wall had a very large convex wood diffusor that looked like room decoration, not treatment.  But, even this room, which I liked, got mixed reviews.  Two of my friends did not like the sound and both are audio professionals.  So much of good sound IS subjective.

At the time I heard it, I too thought the Snell Type B (the big version) was a quite nice sounding speaker--very rich and full bodied and authoritative sounding.  It was a bit overpowering in bass response in the room I heard it in, but, it was quite a nice system.  I do wonder how it would fare after all these years.  I would expect that any reassessment would be more the case of my personal taste evolving rather that the technology being superseded.