@timlub --
Good post, in which you did however only touch upon the amp side of things and not the speakers, which with low efficiency in particular will potentially further complicate issues with thermal compression/modulation as heat build-up in the voice coils, even if it’s only for short periods of time as a rather "dynamic" phenomena.
I might also add that removing the passive crossover between the amp and drivers for active configuration will have the amp(s) seeing a much easier load, with the better driver control and sonic benefits this entails, while also thriving on load independency between the amp channels coupled to their respective driver segments and limited frequency spectrums. So, a combination of high efficiency, good power handling, active config. and sufficient quality power will be among the core parameters to ensure the most optimal outset for dynamic prowess, as well as other aspects in sound reproduction.
As the article supplied by poster @ditusa points to, not everyone is in the need of the same effective headroom (if there even is any to speak of) for their specific requirements and setup context, and so to their needs may be dynamically well served with smaller, low efficiency speakers. That’s however also a clear indication of what's relative to the individual benchmark one sets about to work from, and the importance that is assigned to this specific area.
Tom Danley on headroom and power compression (excerpt):
Well before a speaker burns out, it is severely compromised in it’s performance.
With the heating of the voice coil, one finds the SPL decreases relative to the expected level with increasing power, also the systems tuning / frequency response changes at the same time, for the same reason.
For modern drivers, this power compression begins about 1/8 of the drivers rated power, if rated using the AES procedure.
Honestly there is so much BS regarding specs and such in commercial sound that to add a sense of realism or something to that mess, we have a 3rd party laboratory specify usable rated power. Hifi, don’t get me started.
https://www.avsforum.com/threads/danley-dts-10-super-spud-diy-kit.1189404/post-17409024