I don't ever recall being quite that enthusiatic about the D600 since I returned them (there may be an enthusiastic early post out there that says otherwise), but I did think they were a good headphone with excellent resolution and detail retrieval. I thought their highs were just a bit bright and the lows lacked depth and punch. I consider the M-100 superior in terms of perfectly matching my taste in sound. M-100 highs don't extend quite as far, but I prefer their smoothness. IMO, M-100 really dominates the D600 with punch and depth on the low end. While I could hear the bass of the D600, I couldn't feel it the way I can with the M-100. D600 might have a slight edge in midrange presentation, but M-100 is excellent there as well.
Edited by Craigster75 - 6/13/13 at 6:57pm