Jzbass,
I don't think they're directly comparable, seeing how the M-100 has a closed earcup while the hd600 is open. Val did describe the sound signature of the M-100 though, and to summarize the two main points are that the M-100 is like a cross between the LP2 and the M-80, to have a fun sound signature that will be appealing to the greatest number of people. The signature has the liquid mids of the M-80 but a smidgen less "forward", bass that's tight but between the LP2 and M-80 in presence, a little more treble extension than the M-80 but still non-fatiguing. But that's 2nd hand impressions from a pre-MP sample. Rest assured that the M-100 will extract the detail in a recording and present it in a meaty fashion (filet-mignon meaty).
You're gonna like it, but if you want a direct model comparison, you're going to have to audition them side-by-side yourself when they come out. Take advantage of a store's return policy, but it's a bit silly to ask someone else how two headphones compare so you can gauge which you'll prefer, even more silly when that someone else has been working hard, using years of experience to develop his babies. If you're interested, you'd be doing yourself and Val a disservice if you do anything less than try them yourself.
?
I'll even buy the protective case for it.
