Dynamics In A Speaker

Isn't sensitivity/efficiency a huge factor in a speaker's perceived dynamicism (is that a word ;-?)?

The ONLY relevant factors for dynamics are:

1) sufficient efficiency

and

2) sufficient size.

You need to move a LOT of air easily.

There's no such thing as a small inefficient speaker that's dynamic.  Prove me wrong. :)

Thermal compression is just one non-linearity in moving coil loudspeakers.
Diaphragm misbehavior (due to high stress at high drive) in another factor.
The most common factors are suspension non-linearity (as the diaphragm moves) and magnetic non-linearity (as the coil experiences a varying magnetic flux density as it moves).
Using a very large loudspeaker (one actually developed for much larger spaces) in a smaller space offers many advantages.
For me, the only significant weaknesses in an all horn system used in the home are frequency response smoothness and time and cavity issues.  In the Klipschorn, there is very significant time and cavity issues in the upper end of the bass horn as it mates with the low end of the midrange horn.  
I heard that the most recent versions of Klipschorn are much improved in this regard but still, the bass source is much delayed compared to mids and treble.  
That (and cost) might be one reason most horn systems use more conventional direct radiating bass approaches.