Watts, and clarity.

I have no idea about the scissors but can tell you watts now a function of the amp they are being produced by.  A tube amp generally produces fewer watts but it's sound depends on the output transformer's bandwidth or some technical speak. So your typical SS amp may  benefit from a lot of watts  , but I have heard it said that Nelson Pass says "If the first watt isn't any good whats the use of the rest of them"

The answer is always "It Depends".
Decibel is indeed a logarithmic scale, you can read more about it on Wikipedia: https://en.wikipedia.org/wiki/Decibel
The minimal amount of output watts to be able to hear music at a reasonable listening level depends on the efficiency and sensitivity of your speakers.
The amount of output watts that your power amplifier will output at any given input voltage depends on its gain.
The input voltage to the amp depends on your source and the gain of your preamp.
If you are exposed to levels of >85 decibels for an extended period of time, you are at risk of permanent hearing loss.
Practically, most speakers will produce 85db with only a few watts...
My previous system had Zu Druids which have 101db sensitivity, and I drove them with 1.5 watt SET tube amp and I rarely needed to turn the dial to full volume, that also depends on the source gain.
The benefits many people attribute to having over-powered, hundreds of watts is headroom and dynamic range. That means a powerful amplifier can play a larger range of volumes, and won’t struggle with a loud kick-drum or organ note, as it is far from its limit. Of course, you have to take into account that the input voltage needs not clip as well for that to happen.
Bottom line - follow your speaker manufacturer recommendation, and as a rule of thumb, you will be better off with more power than with less, as clipping of amplifiers, especially solid state is very annoying to the ear and can damage the speakers.
HTH

PS: watch this video by Paul McGowen - https://www.youtube.com/watch?v=hSac09svJuc

I have yet to see a credible proof of the scissor argument.

And it all kind of depends. I don't think absolute wattage matters so much as output impedance and your speakers.

ESLs are among the most challenging, but some dynamic speakers are really tough too. Some speakers which are rather easy to drive don't require as much muscle and would do almost as well with several modest integrated amps now on the market.

IMHO, for small living rooms, with 86 dB+ speakers, 100 Watts per channel is all you will really ever use, and the quality of the amp will matter much more than the watts.

What IS true is that to double the effective volume, you must multiply the power by 10x. So, buying a 200 Watt amplifier isn't all that in terms of clarity or performance. In fact, it will only be 3dB louder.

The Parasound Halo A23's are great examples of modest power (100 W/ch I think, maybe 120? ) with reasonably low output impedance and quite reasonable, slightly warm sounding amps. I recommend them as a starting point for your listening.

erik_squires"I have yet to see a credible proof of the scissor argument."

You and you're "credible proofs" are so funny always demanding, insisting, and requiring that others deliver to you upon your sole, unilateral, and arbitrary demand "proof" supported by scientific data that you accept or reject at your singular discretion while you insist that lack of credible proof reflects "snake oil" "cons" and other such nonsense. Why don't you go do some testing on you're own and then you will have your answers.