What component is responsible for dynamics ?

The more sensitive the speaker the more likely the noise floor will be higher, and the softer end of the dynamic scale will more likely to be negatively affected.

Charles1dad, It would appear to me that high efficiency speakers are often more huge in comparison to low efficiency speakers, than mega watt amplifiers are huge in comparison to low watt amplifiers.
It appears as though, very often high efficiency speakers cost more and offer less extended frequency response than comparably priced low efficiency speakers. Furthermore, it appears to me that many systems that use high efficiency speakers use amplifiers that have lower watt output, but those amplifiers often actually cost more at purchase and there after. All in all, IMHO, high efficiency speaker systems appear to offer less value. As such, I disagree with your assertion that "...high efficiency speakers would be a very good and logical place to start,...).

I couldn't agree more!:-)

Chadeffect, with a lower sensitivity speaker you will end up with less noise at lower volume levels, and a much better chance at having a true time and phase coherent sound. I am still waiting for a high sensitivity speaker that can demonstrate the ability to pass anything resembling a square wave. The only thing a high sensitivity speaker does better is providing more ultimate volume in larger spaces with less power. Not something that most residential users tend to need concern themselves with.

Chadeffect, square waves aren't the end all, but certainly are an insight into fidelity. We wouldn't accept the inability of an amplifier to produce a square wave, why would it be any different for a speaker. Some traditional dynamic, electrostatic and even true Walsh omnis speakers can do it, but I've yet hear of a high efficiency speaker that's capable of it. Seems to me that in the effort to gain high efficiency, sacrifices have been made.
I think we sometimes have different priorities, which explains the different audio systems. I would choose correct time, waveform fidelity and lack of coloration over the ability to produce volume levels well over 100 DB for my home. To each his own.

JohnK, is English your primary language?

Tbg, because he seems to constantly misread my posts.

Thank you for proving my point.