The way I look at it, the better your system, the lower the volume you will be able to listen to it at w/out the need to feel like you want to turn it up.
Systems which are not balanced and musical have certain frequencies which usually get to us, whether it be the midrange or the sibilance, or really muddy bass... we're looking for a certain feeling, an impact... certain frequencies we want louder. I noticed this in car audio especially, since some of the desired musicality gets lost with all the road noise and poor car audio speakers/sound reproduction in general. So people tend to turn it up to solve this.
This of course can lead to certain elements fatiguing and eventually damaging our hearing (they are louder and more harsh then they should be, but the volume level feels right). Anyway, I used to always listen quite loudly until I figured out how to get my system to be Euphonic and Very Resolving. Now lower volumes suck me in and I don't feel a lack of absorbtion at these levels.
Neil