Once you hear it...you will understand what everyone is trying to tell you in this thread. When the sound gets muddy and/or harsh and those conditions are alleviated by turning down the volume, that is the distortion, either from the amp and/or the speakers, that you want to avoid. It is possible that some of us learned this the hard way...in younger years perhaps....by blowing up components. If you haven't done that yet, you could be well on your way

But like I said, once you hear it, you will know it and then you will stop obsessing about meters for any purpose other than their real one...which is eye candy.
The approach you are wanting to implement seems logical given that meters exist and speaker power ratings exist. But the ability to use these things in a useful way, at least in a precise and useful way, is an illusion. For one, the calibration issues already mentioned several times. That and distortion happens in both speakers and amps and even if by using meters to avoid amplifier distortion, you still need your ears to be listening for speaker distortion.