high-efficiency loudspeakers

 "The Best" is a moving target.

*S*  Absolutely...typically, what you have....until you fall out of love with it when 'Better' appears....

wolf_g, yeah, and the Edison cylinders just complete the Experience.....  (...the crystal tuners' whisker forces one to turn off the Mazda lamp, which invariably knocks it off signal....as a source, a notable fail....*sigh*....) 

Classic Audio Loudspeakers T3.4 or the Bigger Brother T1.5 Field Coils.
Dynamics are scary, the speaker is so fast, smooth, and emotionally engaging.

Over the holidays I took delivery of a pair of Daedalus Audio Apollos. Far and away the best speakers I have ever owned and among the best I have heard at any price. Simply gorgeous and sound incredible. I have done some writing about them here:

 https://forum.audiogon.com/discussions/daedalus-audio-apollo-speakers

and will continue to add impressions to the thread. Very efficient, easy impedance load, high power handling, easy to place in the room, big, bold, natural sound. I am running them with an LTA Ultralinear amp which is a great match. 

I have a pair of Shindo 604 Field Coils at 16ohms/101+sensitivity. They are pretty special and I don't see moving away from them. I also don't see moving them period as they're the size of a washer/dryer set.