My only response to your questions ... I loved my 804N and 803N speakers, but at low volume I was forever disappointed. Those speakers came to life when driven with some watts ... I don't mean knock-down-the-walls watts ... and at volume they were incredible. At low to lower volumes, as when I wanted to read without having the music compete, the B&W's simply didn't satisfy me, nor did they reveal how wonderful they were.
As someone else pointed out, the transition to big music from small music was incredible, as the B&W N's would create a bigger sound without breaking apart ... not in a "loud" way, though they would get "loud," but rather in a "bigger" way. Great music from smallish speakers.
So, I'd counter that being able to use "volume" is essential, especially if a particular speaker actually sounds amazing at higher volumes. Such speakers don't always satisfy at lower volumes.