#1
I've heard this expression used multiple times to describe the threshold amplitude at which you get a balanced, driven power amp tone. I was wondering if things like low wattage amp heads could acquire dynamics and responsiveness similar to this at lower volumes with certain modifications.
#2
Most amps do need to be turned up rather loud to be at their most dynamic, and even for low wattage amps it's usually a loud setting. The speakers themselves need a certain amount of energy behind them to get the dynamic range we usually desire in a guitar amp, so it's difficult to rectify that with the a low volume solution. Power scaling can fix the volume issue for nearly any amp without much effect on dynamics, and some well designed master volume controls can do the same. Still, the speaker is often a limiting factor.
#3
How does power scaling circumvent the lack of drive on the speaker? Or does it simply manage to put a lot of power on the speaker without most of the energy being sonic?
#4
this is a bit late but have you googled de-tuned speaker cabs? this isn't something i know anything about but ive stumbled across it briefly while looking up power scaling amps.

meant to give more of the sound and "loudness" (bass, definition, balls etc.) of a cab driven hard. however, apparently they don't cope well when actually played loud. i.e. ideal for people who have to powerscale down to whisper level

like i said, i dont know much about it but a quick search; it may be what you're looking for.

PS - power scaling actually reduces the energy to the speakers