I feel exactly the same about the UE6000. I also returned the D600 because there was something I didn't like about their bass presentation that I couldn't put my finger on. For my taste, the M-100 is sonic perfection with highs that extend further than UE6000 (not as bright as D600) but are incredibly smooth, detailed mids and some of the tightest, deepest bass I have heard that doesn't overwhelm the music.
Hm, might have to give those a try then. How does the soundstage/imaging compare? and are they much bigger than the UE 6000's? cause the UE's were about the biggest I would want in a portable. Right now I'm messing around with Amperiors and a DT1350 cause I like the portability factor, but I'm not entirely satisfied yet I think.
And yeah, I really think it's the mids that make the bass seem odd on the D600's. Just look at their FR graph, there's like a random abrupt drop right there in the 300hz region. If they had just even slightly better mids (i.e. smoothed out that silly drop) and didn't even bother improving that dubious treble, I think the D600's would've been regarded much more highly than they are; cause the pure bass and sub-bass response on it's own I think is top notch. Unfortunately Denon decided it was ok to butcher the rest of the frequency range, so now I'm stuck waiting for Fostex to release their TH600 to see how those are.
Edited by oblique63 - 1/23/13 at 8:47pm