Loudspeaker sensitivity and dynamics: are the two inexorably linked?

I like some high efficiency speakers for how lively they sound at LOW average volume.  That, to me, is more important than dynamic range—the ability to play at both extremes.  There are not that many high-powered amps I like a lot, in particular, I don’t care for most high-powered tube amps because they tend to sound hard and have an unpleasant “glare” (sharp upper midrange peak) I don’t like.  High efficiency speakers and the modest volume levels I prefer allow me to use the 10 watt or less tube amps I like the most.

Bobbyd,

“I'm not referring to maximum loudness or volume, rather that the music sounds less reproduced and more that the instrumentation and vocals are more real sounding through higher sensitivity speakers.”

this is my exact experience when moving to horns. I don’t see myself going back as I have learned that dynamics is what I was missing. 

Efficiency is simply how loud a speaker will play at any given wattage, but is measured at 1 watt. It has absolutely zero to do with how it sounds. Magnepans are not very efficient but sound glorious. 

Magnepan's sensitive and dynamic?! I like Maggies as much as the next guy, but those are not two adjectives I would ascribe to them. In fact, Maggie detractors have long found them lacking in exactly those two areas. They are in the range of 82-84dB, and require huge amounts of current to "come to life".  

@cleeds 

1+ There is no connection at all. Good examples are Horns and ESLs two vastly different types of loudspeakers. Horns are very efficient while ESLs are not. Both are very dynamic in the portions of the frequency range they can handle correctly primarily because their transient response is so fast and they are not spraying sound all over the place both being very directive in specific patterns. An excellent example of an instrument that both get right while other types of speakers struggle is the snare drum. Both ESLs and Horns have limitations in terms of frequency response requiring crossovers and low frequency support. While you can make a bass/subwoofer horn, the size requirement is extremely prohibitive so most horn systems revert to regular dynamic drivers. ESLs do well down to 100 Hz then suffer greatly actually limiting their dynamic potential. Supported by subwoofers people can't believe how loud an dynamic ESLs can get. Just ask skos.