Sorry, I checked two of your three links....

Here's my opinion on the topic, sort of distilling what the guy at that site said: Power doesn't kill, misuse of power does.

So. If your amp is underpowered, and you want it louder, so you crank the volume so hard that the amp's input signal is overdriven, then you cause clipping, which is Bad.

If your amp is overpowered, and you inadvertently turn things up loud enough so that it causes too much energy to go through the speaker's voice coils, thus causing the speaker to clip or the voice coils to overheat, then that is also bad.

I'm not sure which is worse or which is more likely to blow a speaker.