Hello Dave,
There is very little chance that there is any nuance difference between the three Denon AVR’s you are questioning. You can measure the quality of an amplifier, but “sound quality” is subjective.
You may measure the quality of the amp and its circuitry, and then listen for any improvement in sound quality the hardware MAY provide.
Sans any consideration to greater functionality, these three AVR’s, I would guess, are identical in terms of overall sound. (Of course any amp will distort if overdriven)
One might be able to calculate approximately what an amplifier may sound like from its measurements, but measurements can be deceiving when you try to match them to sound quality.
The difference in volume between these AVR’s is slight at best, less than 3dB between the 1909 and the 3808. Further, SPL has no relevance to sound quality, and is mainly used to describe speaker sensitivity in this context.
Enjoy the music
