The Best Sounding Systems can Play Loudly with Low Distortion

I agree that the very best systems are impressive at how softly they can play and still sound alive and vivid.  This is the case with gigantic horn systems.  This ability is far more important because most listeners listen at modest levels most of the time.

While horns have the ability to play at very high volume levels, there are some other great speakers that are very limited in loudness capability, such as the Quad 57 electrostatic—cannot do deep bass, limited volume level, yet sounds so right.

Don't forget proper room treatment! It doesn't matter how good the system. An untreated room is easy to overload rendering it unlistenable.

Indeed. The problem of course is you don't really know how loud your system is playing if there is no distortion. A DB meter is handy. At work we used to have a 1% THD button on the test kit. It always made the listener perceive it was louder.

I recently heard a massive Klangfilm system centered on Bionors. It had an ease and seamlessness that made listening unfatiguing at much higher volume than I do at home. But the room was expansive, huge; it had a natural decay that did not interfere with the sonics. The system is far different than the inert boxes delivering a forensic "audiophile" sound with all the attributes-- really more like a giant wave, on a huge scale, that was faultless in tone, dynamics and range. Very interesting experience for me despite my many years at this-- not something that would be easily achieved given the the components or the level of attention required to operate and maintain such a system. Absolutely glorious to hear though!