I do seem to think that for the 60s to really hit stride they need to be turned up a bit to give that openess.
That was my finding as well. I found the M60s sounded much more like the M80s once the power was turned up a little, say in 80 - 85 db and certainly higher. The M80s really shine at lower volume times, where they still offer that great detail and an open/airy sound while the 60s sound compressed, slightly muffled, much more like almost any other quality speaker out there; but as most people seem to listen in the 80 -85 db range where there isn't much difference, just the slight differences as noted before.
