Sometimes Hard to Drive Speakers are a Gimmick

Evidence of what? 

Name these 3 candidates. 

Hi Erik, I think a most famous amp burner was the Infinity Kappa 9 with essentially a reactor in the woofer circuit. Huge capacitance in series and big shunt coil.

In crossover experiments, I can't escape the fact that complex crossovers have an audible penalty of truncating the decay and making each driver only carry an unnatural sounding limited range. So your ear has to stitch together the sound.

Another strange thing I had found was that wiring identical drivers in series makes the imaging drift and it was better to parallel and add resistance. Apparently the inductance of the voice coils creates perhaps a phase shift favoring one driver over the other in complex waveform.

I have never heard a 4th order I liked, the less you can get away with the better. Also each shunt element is consuming amplifier power and making back EMF to some extent. Speaker building can be the most frustrating yet most rewarding thing when it finally dials in..

@audition__audio - Seems like you actually skipped my post and the blog where the data is kept.  Maybe start there. 

Efficient impedances are generally a good thing, but it does not replace the higher goal of personal sonic preferences.  

Inefficient impedances does not “logically” lead to a conspiracy of speaker manufacturers with amplification manufacturers.  There is no proof.  There is no motive.  Rather, manufacturers simply make products to work with other products readily available in the marketplace and that includes flea watt to high powered amplifiers.  Their efficiency only needs to reach “good enough” vs “optimal” which may cost more time, expertise, and resources.  

Speaker manufacturers do not determine amplifiers wattage, it’s the market that determines what is in demand - speaker manufacturer does not have a monopoly to control anything.

The OP is looking inward to draw conclusions of the outside world rather than seeing how the outside world functions.  
I’ve been to the Magico manufacturing headquarters- they use cutting edge equipment, technology, engineering, and materials to design speakers to minimize errors.  Efficiency is only one element in their design decisions.  Some low watt amplifiers may not be able to fully drive their speakers, but that’s not their target market- there are plenty of capable amplifiers available.

@kennyc  I agree, some people still desire the old Apogee scintilla speakers that hover around 1ohm and are 78db sensitivity, but they love the sound of them.