I would assume the M100s were competing more directly with the DT1350, although offering a different sound. The DT1350s run under $300. I don't know anything about the Amperior sound-wise but it just looks like a metal HD25 with an iPhone cable; another rebrand attempt by Sennheiser.
Why would you assume that a full-size headphone is designed to compete against a smaller/portable headphone? I believe the M80s were designed to go head to head with the models you mentioned. So, perhaps, Val would think since he's already addressed the audiophile crowd seeking something portable that now he should focus on something not quite as portable.
Anyway, I sure hope Val chimes in soon. All this speculation will be for naught when he comes back and says he changed his mind and is deciding to turn the M100s into IEMs instead :P