Suggestions for high efficiency speakers?

Kirtgunn mentioned engagement, yes, this was what hooked me on first listening to stock Klipschorns in my system. Part of this engagement for me was this uncanny sense of live performers in my room, something I'd not heard prior with the many speakers I'd previously owned.

 A number of years later, the Klpschorns are now after umpteen modifications  like a living, breathing entity brought to life by an elixor of SET amps, DHT preamp and  high resolving source. I'll never leave my horns.

Before I purchased my speakers, I went on a one year cross country (east to west) speaker hunt.  I owned Wilson and Sonus Faber speakers prior.  I attended many audio shows also.  I never thought in a million years that I would end up with a horn speaker until I heard one in the same room with the likes of Eggleston, Stenheim, Meridien, Vandersteen, Vivid  and KEF.  The horn was Avantegarde.  From that point on I searched only for Horn speakers.  I considered Charney, BD Design, hORN, Avantegarde, Deja Vu, JBL, Klipsch, Tune to name a few.  Then someone mentioned this boutique horn builder in Sante Fe, NM called Viking Acoustic.  I went to the builder/designer's studio and was immediately impressed.  I ended up buying the Viking Grande Voix Dual horn speakers.  They blew away my more expensive Wilson and Sonus Faber speakers.  While the GV's may be over your price range, they do have many speakers in their line to consider.  You should give David Counsell a call at Viking.  

There was a pair of Emerald Physics 2.8s (open baffle) original MSRP $10K, now discontinued you can buy for ~ $3K on a competing used equipment site

Highly recommended

I was also impressed by the Audio Note's in Deja Vu's room at the Capital Audio Fest and also agree with your impressions.  I thought it was the best sounding room in my price range until I went to the Volti Audio room.  I listened to both the Rivals and the Razz that day and was absolutely gob smacked by both.  I insisted that my crew of friends listen to the Rivals yet again and they agreed that the Rivals  trumped even the excellent sounding Audio Notes.  I cam back and listened to the Razz later that afternoonr after again stopping by to listen to the Audio Notes.  I then spoke with Greg Roberts at the end of my day - very nice fellow and obviously passionate about his product.  He agreed that the Rivals were likely too big for my 12 x 18 listening room.  I ended up ordering a pair of Razz after a few days consideration to replace my Harbeth 30.2s and my REL sub, which until I have REALLY enjoyed.  However, the Volti sound has a presence and natural sound that just grabbed me.  The Volti's made me feel like I was in the middle of the music!  After 40 years of listening/buying and selling toomany speakers to count, if the Razz can do in my room what they did at the Capital Audio Fest, they might be my final pair of speakers.  I'll be running them with a Rogue Audio Stereo 100 tube power amp and a Prima Luna EVO 300 preamp and worry that i have too much power for the Uber efficient Razz given that Greg was running them with a 20 watt Border Patrol amp.

I liked the Volti room too, but, they had a little bit of a problem with bass response (probably the room and show conditions)--the bass was not well integrated with the rest of the sound.  Still, the old school technology (horn drivers, tube electronics) was quite impressive at the show when it came to just presenting music.

You will probably have even better sound in your own home, given that you will have more time and resources to make the speakers work well for you.