Efficient speaker: Zu, Tekton, Volti, Klipsch, Fleetwood?

After watching this video, I am changing my mind about Klipsch

https://www.youtube.com/watch?v=EKxOWKQewVs

https://www.youtube.com/watch?v=sSkIHVJ6rts

Also a video on the Fleetwoods

https://www.youtube.com/watch?v=a5F0bYAa1Fg

I have listened to Tektons Ulfbehrt’s (or whatever the monster 7’ speakers are called) sides by side with Zu Druids.  With the right amp, setup correctly, the Tekton’s are very good.  That being said, they are harder to drive than you would think as the efficiency deviation is driven by them being 4 ohm speakers.  With the wrong amp, they sound bad and picking the right amp is harder than you would think.  At least for these giant Tektons.  A high current tube amp with 4 ohm taps can do the job well.  A SS like Naim would be a better choice.  
 

regarding impedances actual impact beyond making it more taxing on an amp, in practice it may have minimal impact unless you listen at very high levels or are using for home theater.  With 20w of power, a 92dB speaker will output 102dB of volume at 9’.  A 97dB speaker will output 107dB at 9’.  For music, 10-15dB of headroom is plenty and since reference levels are 85dB, there is no practical difference other than where you have the volume nob set. 

To my taste, especially with a lower watt (20w in triode) tube amp, I preferred the Zus but the Tektons sounded really, really good with that amp.  Really a matter of personal taste.  
 

Tannoy Kingdom Royal MkII

4-way bass reflex, 8 ohm, freq. response 24Hz - 61 kHz (-6dB), sensitivity 96 dB for 2.83 volt at 1 metre, 90 deg conical dispersion. 

$40,000.00 each from Stereoland, Bloomington, MN

I think the titanium driven mid horn in Heresy III sounds better than the new poly driven and much simpler mid horn (the convoluted deep throated mid loading Heresy III horn is a very different design relative to the simple short throat IVs) in the heresy IVs. That said, best 1500 bucks I’ve ever spent (open box or something non sequential serial numbers new a few years ago Capitol Records 75th anniversary version). Clean and clear alleged 99db masterpieces I’ll likely never get rid of. 2 REL subs flesh out the lows...do they sound better than some of the far more costly options noted here? Meh...just don’t care...most other new efficient speakers are either ugly, expensive, or both.

I never heard any of them but if you randomly reorder the list, I can tell you that #2 and #4 are terrible.