My experience has been how well a system performs at low volume is hard to pin exactly to the source. However mine has gotten better and better at lower and lower volumes the better my system has gotten and now I happily enjoy 65 - 70 db. At this volume I get the fully nuanced and dynamic sound I crave. When playing a symphony I adjust it to where the sounds just barely audible coming from the sound floor are that, and crescendos are at the upper limit of undistorted hearing. But symphonies have the highest dynamic range.
From your descriptions of what you value in sound quality suggests that an equalizer is your solution. You want it to sound loud when it is not. If I were you, I would get the best quality equalizer you can. Folks that love loud music tend to appreciate the dynamics and force and not so much the nuanced detail… so the equalizer will improve what you love and not effect what you don’t.