The D1100 sound NOTHING like the AHD1000/01 a major downgrade in sound.
As far the poster wanting to know if the Cal/Denon are an upgrade to the M50's. They aren't even in the same room. The Denons do everything MUCH better. But you will have to find a 1000/01 used as they are about 2 series ago. The Cal uses the same Fostex/Foster driver but DO sound different. They are very close but the Denon's sound a tad better, maybe due to the cups/cable being different?
Now the D1100 will be a side grade to the M50, I think they are better myself, but the build leaves a little to worry about. The forks are very fragile.
Sorry for the confusion what I meant is the cal! And the d1001 sound simIilar. And I have heard the d1100 which is the newer d1001, and I never heard the d1001/cal!. Which I found out by you now don't sound anything alike.
And everything else you said about the d1100 and the m50 is the same as I how I feel being more of a side grade.
The d1100 bass is overly done and over power everything, to me they sound all over the place and slightly confusing sound.