High power amp, does it matter at low volumes?

Per Welcher, I normally listen at a max 65 dB, at my seating position. Mostly rock, blues, some lighter music like Jesse Cook.   

If I understand everything correctly, I am using 1/4 watt of power to get 65 dB at 12 ft ( I added a bit of distance ).  Adding in the dynamic factor for rock, normally what I listen to, guys like Tommy Castro, I get 108 dB spl at the speaker, which works out to 64 watts ( to handle the dynamic range ).

Some fascinating information here.  The 3 dB rule gain for double the power. 6 dB rule for double the distance. I don't remember ever hearing any of this..

So, what I am getting from this discussion is I would need atleast 64 watts ( with that extra distance of 12 ft vs 10 ft ) and I would run my amp at full output, if I bought an amp rated for 65 wpc.  Of course, buying an amp at 120 wpc would mean I would run that amp at half power, a 250 wpc amp at 1/4 power, etc.

I suspect the next factor is running anything at near it full rated load has drawbacks.  Hence, using a high powered amp at lower power is preferable.

I have always thought working the tubes a bit makes them sound better.

Also most potentiometers degrade the sound at lower settings. Stepped attenuator maybe not.

SET amp for low volume.

SET amp will poop itself with B&Ws.
B&Ws need current. It’s not complicated. An amplifier cannot produce current if it doesn’t draw significant amounts of power from the line. It might not be a high wattage amp but if it draws the needed power from the line to produce current required for these speakers you’ll be fine. 
 

If you're listening at low volume, wpc doesn't matter in the least and neither does the type of amplification. Class A, G, D, etc will have no effect on the sound. In fact, even a "flea watt" tube amp will supply enough power to produce low dB music but if you get the urge to crank it, you'll be limited with how loud it will get.

Speakers are not point sources, and the room is not anechoic, so the drop off over distance is much less than the 6dB to double the distance.  That is for a point source in an anechoic space (e.g. free air outside). I get about 4 dB drop off at my listening position.

At 65dB you are never going near 1 watt.

My speakers are 87dB at 1 meter, 2.83 v.  I played a 440Hz (A4) tone at 65 dB at my listening position, about 12 feet from the speakers.  I measured the voltage at the 4ohm Rockport Atria II terminals.  0.172 volts.  About 7.4 milliwatts. 0.0074 watts.  At 2 volts, = 1 watt, I was at almost 83dB (using hearing protectors) 12 feet from the speakers.

Do not spend money on more watts!