Interesting. I think the bass is somewhat bloated on the M-80, it's certainly not tight and controlled. And when you couple that with it being rolled off up top, I can see why it may appear bassy to some. I'm sure the M-100's will improve on comfort moving to a circumaural design, but unless they tighten up the bass and add even just a little more detail, it's the same ol' same ol' (soft) mediocre headphones.
I actually didn't find the bass loose and bloated at all...what sort of source are you using?