One of the things I learned along the way is that there is a really big difference between tubed amplification and solid state. For solid state, more power… of the same quality make most speakers sound better at most volume… even at nearly a whisper. This is also what is “said” in audiophile circles and it is typically very obvious unless you have very efficient speakers… then it can be a liability. Why? I have not really found investigating why results in a means of determining if speakers match amps other than at the most general way… like don’t pair a 2wpc amp with 82db efficient speakers.
Most speakers are much less sensitive to the overall power from tube amps… quality is more of primary concern… so I used to use a 350wpc SS amp to power my 90db speakers and dropping to 250 wpc would make a difference. I replaced it with a 140 wpc tube amp and they sound very different (the tube amp sounds way better… and different). I can operate my tube amp at 140wpc or 70wpc in triode mode and there is virtuallly no difference in volume or punch, but the 70wpc sounds better and more musical. Why? I have not really found investigating why results in a means of determining if speakers match amps other than at the most general way… like don’t pair a 350wpc amp with 100db efficient speakers.
So after fifty years of passionately pursuing high end audio what is my conclusion? If you are trying to come up with a set of specs that will lead you to the right choice of amp forget it. You must try them. However, if you are simply interested for the sake of learning… carry on… good luck. But still make sure you audition amps first… especially if you have a big spread in the sensitivity / amp power.
Also, one of the most amazing / interesting systems I have heard was a huge panel electrostatic powered by a 4 wpc Viva tube amp. Which was the most ridiculous pairing that would never be something that theory would have led you to put together.