For me it’s all about Dynamic Range, not loudness per se...
Well, that me be your (Geoff) preference, but there certainly is more to it than dynamic range. For example, one could choose to listen to Tchaikovsky's 1812 Overture or Ravel's Bolero, each of which have reasonably high dynamic range. If you then choose to "top out" the max decibel level of that dynamic range at say 80db, you've done an injustice (IMO) to the great work of those composers. So again, volume/loudness *does* matter.
Geoff, you should be impressed. Looks like I know about and have listened to more music than only Grateful Dead :)