I looked into it and just for fun , estimated the power requirements for the +20db peak, over reference level(85db), for my listening distance and speaker sensitivity of 91.5dB...and the required power estimate of 70.7w for speaker with 8 Ohm nominal impedence and 141.5w for speaker with 4 ohm minimal impedence
That is where your calculation is simplistic.
Moving coil speakers don't present a simple resistive load.
Not only will the minimum be well below nominal there will be phase shifts too.
This is where the difficulty comes.
There may be 2 amplifiers which are quite happy delivering 100 watts, say, into a 8-ohm powert resistor on a test bench but one of them may clip when the impedance drops and the other not.
It is a fundamental flaw in the testing of amplifiers in the English language press.
As far as I know there is no way from published data, either of the speaker impedance or how a given amplifier may respond to that particular speaker in terms of power output or stability.
Looking for flat tops in the signal on an oscilloscope connected to the speaker terminals will show if clipping is taking place but that is only valid for the amplifier and speaker being measured, it can't be translated to general conclusions.
The main thing is that some speakers are extremely brutal loads. One could argue that good speaker designers take the load into account and some do not.
The ones I know about are Harbeth, which are all easy loads, and Wilson, none of the ones I have seen plotted are.
One would expect Harbeth to perform well with any amplifier and Wilson to need a welding station to power them.