Thanks for these impressions. As these are not available locally for audition, I think I'll take a pass on just those two criteria. So thanks from me and a curse from Sennheiser :)
The search for truly non-fatiguing, excellent wearing-comfort and bass-capable portable headphones continues (please let nobody suggest the DT1350. Been there, done that, didn't work for me).
Ah well, maybe the Momentum is a decent compromise. We'll see. Or hear :)
If you can try an HD 25-II, which many stores stock, that'll give you a great indication of what the Amperior sounds like - from what I understand the Amperior and HD 25-II sound pretty much the same. :)