I do most of my listening at low volume levels in a nearfield setting (>12 hrs/day), so I have experience with this. A couple observations:
- It's true that some speakers sing better at low volume than others. I've had a run of sealed/acoustic suspension speakers that do this very well. They were all 2-ways of varying size: NHT M-00s & matching sub (powered); ATC SCM12 Pros (passive); and vintage KEF 103.2s (passive). Currently I'm using a front-ported design that also sounds quite good at low volumes, the Harbeth 30.1s. But I've also had speakers here (all ported, whether passive or active) that sounded terrible until cranked.
- Same for amps. I'm on my 2nd class D amp (Bel Canto 600M monoblocks). The first was the Wyred 4 Sound ST-500 stereo amp. Very different designs with a few sonic differences, but both sound great at low volumes
- And a recent discovery, more or less by accident: I have a TVC (transformer volume controller/preamp), and when I use it as a trad preamp with the volume pot set very low, the sound coming out of the speakers is even more expressive and dynamic than I'm used to. I'd read about this, but wasn't prepared for how true it is. At higher volumes the sound is not anything special, but at low volumes, it's definitely special
The biggest factor is luck. Really. I just got lucky to land on gear that sounds great at low volume.