Hi L. Chung,
I haven't burnt a speaker yet, and I have driven many speakers with clean unclipped power with music, not sine-waves, far beyond their continuous max power ratings. :lol:
Dynamic headroom is "music power". It is the extra power above its continuous full-power rating the amplifier can provide for a moment before the unregulated power supply voltage sags. It is rather meaningless because they don't say how short a time before the voltage has sagged (it starts dropping immediately and exponentially), and you don't know how long a sustained full-power phrase in the music will last. It might be good for gun shot sounds, but 2.1dB is such a small increase that you won't know the difference.
Even speakers have "dynamic compression" at high power when the voice coil heats, its resistance increases, reducing its power a little until it cools. :lol: