I listen a lot based on the volume that one would expect if the music was live. So with Wagner- peaks around 110, but ELP's first LP I'll have dialed back a bit to peaks at 100-105. Solo guitar is then at 75.
In order to play these volumes comfortably (the way real music can do- 110 db is easy for a live orchestra), the system has to be free of resonances and odd-ordered harmonic generation (odd ordered harmonics are the cues that the ear/brain system uses to determine how loud a sound is). With no artificially enhanced volume cues then the cues come from the sources rather than the playback.
In order to play these volumes comfortably (the way real music can do- 110 db is easy for a live orchestra), the system has to be free of resonances and odd-ordered harmonic generation (odd ordered harmonics are the cues that the ear/brain system uses to determine how loud a sound is). With no artificially enhanced volume cues then the cues come from the sources rather than the playback.