high-efficiency loudspeakers

Yes, currently using Hawthorne silver Iris drivers in a open baffle, sounding very very nice now as my kt77 gold lion tubes in my amp have settled in very nice.With high efficiency speakers I recommend all tubes or tube pre and SS amp.Most of these speakers have horns or compression drivers.For me I won't buy a horn loaded speaker but you may like them .

I have Horning Eufrodite Ellipses which have 98db efficiency.  They sound really well with my Frankenstein 300b monos and First Watt SIT-3 amp.

hocheye  Hawthorne uses a horn loaded coaxil so you did buy a horn speaker

One thing about the Heresy IIIs that's interesting and noticeable when looking at them (which I often do since they're in front of my eyeballs when listening) explains part of the musical coherence they display in spades...measured from the center of the tweeter horn to the center of the woofer is only about a foot...to the edge of the woofer much less of course...all due to the mid horn being narrow top to bottom and placed right on top of the woofer (even has a cutout in the same radius as the woofer to help in the proximity), and the tweeter horn right on top of the mid. For a 3 way that's pretty close, and the design works amazingly well with tseamless blending of the drivers...a good thing.

I am a fan of many high-efficiency systems, but, most are systems built from high efficiency drivers and custom cabinets and crossovers and not complete packages.  I like some vintage drivers and a few modern drivers that are either straight out replicas of old drivers or are modern updates of old drivers; these however, are crazy expensive (e.g., G.I.P, Cogent, Goto).  

Of the modern, complete systems, my favorite are the Charney Audio systems utilizing full range drivers in back-loaded horn configurations.  Until I heard the Charneys, I did not think that a single driver system could really be a complete speaker capable of playing all sorts of music very well.

For a fairly low-cost high efficiency system (albeit with a built-in amplifier for its bass driver), I like the Rethm Bhaava.  At a substantially higher price level, I like the Avantgarde systems that also use powered bass drivers.

For not so high efficiency speakers, I like the entire line of Audio Note speakers, The 093 family of Devores, Trenner and Friedl speakers, Classic Audio field coil driver speakers and Horning.