With the Sennheiser Momentum, there's good news, good news, and bad news. The bad news is for people who would not like the rolled off treble (somewhat recessed compared to Amperior and my other hi-fi 'phones) and who also will not try a treble boost for whatever reason. I doubt that many people will fit both of those, so maybe no bad news after all. The first good news is it has the detail and warmth of the Amperior, but without the excess emphasis and boominess in the upper bass the Amperior has. The lower bass is rolled off some, down perhaps 3 db at 50 hz and 6 db at 30 hz. The Amperior I would rate as marginal for bass-heads, but I don't think the Momentum would be interesting to bass-heads at all.
I like the Momentum. The look in brown leather etc. is nice, like a deluxe wallet or briefcase. It's incredibly light for its size, and I have some lightweight headphones. Count me amazed. It does not completely surround the ears (my average or better size ears), that is to say it's circumaural, but it touches the outermost part of the ears, yet it's soft and comfy. I'm also wearing glasses and no issue there. Most important, I'm playing a bunch of tunes now, not for testing but for pure enjoyment. It sounds fairly spacious for a closed headphone - excellent!
I can't imagine who this Momentum is aimed at. The recessed treble says younger, but the near-neutral bass and un-fashion look doesn't seem to fit that, especially at $350 USD.