Watts! How many do we need?

I would be curious to know what actual volume you are listening at? A crude app for your phone will tell you peaks at your listening position, and if you are feeling inquisitive, you can measure at 1m from the speakers. 
 

1 watt at 1m will give you 86db from your speakers. It’s math. As was stated above, every 3dB step  above that, will require a double amount of watts.

The other thing, is higher powered amps, have bigger power supplies. They will have more power in reserve at lower watt output.

Provided the transistors, and the topology of the amp is such that it is operating in a linear manner at low output, they will sound “better” at low volumes than a lower powered amp with an inadequate power supply.

Which brings us full circle back to Nelson Pass, and the relevance of the first watt.

Peaks are between 75 and 80db. I’m sitting and measuring about 8 feet from the speakers which are 7 feet apart. They are almost 3 feet from front wall and are 5 feet from side walls. Plenty of opportunities for sound absorption. The room is 17 x 15 and is carpeted and is not what I would call a live room as it has furniture as well. The peaks are as loud as I would want and doubling the loudness would apparently require 2 watts. When would I ever need 10 watts let alone 150? BTW these peaks I hear are produced effortlessly with a balanced presentation. No instruments or frequencies are emphasized. It’s a smooth delivery. 

The 1.5 watts of “audio magic” of the 45 tubes is plenty for me. My backloaded horns are 102 db efficient. Korneff integrated amp with Emission Labs 45 wire mesh tubes. Although I must admit that I cheat. With organ music I turn on a Velodyne 18GS subwoofer that has a built in 1500 watt solid state amp. Go figure…

I doubt those meters are able to measure actual peak power, it gets difficult to measure when a speaker is involved. 

The meters found on most amps are very rarely calibrated, and more often mislead rather inform.