Val,
I'd like retract my earlier statement about the M-100's being unamped.
I feel that the drivers should remain the way they are. How significant is the SQ between the M80 and M100, both unamped?
The M80's already have great SQ. They are limited as shown by the use of an amp which make too much of a difference.
If the M100 do not need an amp, the maximum potential would be limited. For $300, I believe the M100's should not be restricted by the driver and it'd be a great set up if you can show your full ability to make headphones to the best of your ability.
For $300, I would think that people considering headphones in this price range would 1. already have an amp 2. have no problem spending $20-30 more for a portable amp (e5, e6) to achieve maximum potential.
For $300, the only portable competition I really see is the Beats Studio and I'm pretty sure the current M100 prototype sounds much better unamped.
In terms of bass, I think your idea about the M100's bass being heavier than the M80's but less than the LP2 is spot on, as long as the bass remains clean and more mid-bass as opposed to sub-bass. For example, the Pro 900 is very bassy, some say the king of bass (mostly punchy mid-bass), but the bass is of excellent quality as well as the rest of the frequencies being of good SQ. And despite being very bassy, it doesn't drown out the other frequencies and I haven't seen anyone complain about it's bass.
I also think that the Beats Studios would be a direct competitor, so it should have some type of bass to compete.
I also think that since DJ's would be using these headphones, bass is important as you probably know from the feedback you have received from other DJ's.
**
When looking at the dilemma between amped and unamped, I think about Porsche. The 911 is more expensive than the 987 (Cayman and Boxster S) lineup. Even though the 987 is cheaper, it has superior engine placement (987=mid-engine, 911= rear-engine). The mid-engine design gives the 987 the best balance and handling. Because of the superior engine placement of the 987, Porsche has limited the hp output of the engine in fear that it'll outperform their legendary 911-model.
In short, many people have complained that Porsche has manufactured an astonishing car with an excellent platform that has the potential of being nothing short of perfection. It's only downfall is that it's limited by the horsepower.
@ 4:57
http://www.youtube.com/watch?v=ppl4DFcRCPA
"You get the impression that the Coxster could have have been made faster and better, but the engineers weren't allowed to, cuz then it would have been faster and better than the 911. So the Coxster then isn't quite as good as it could have been. I couldn't live with that. I like to think that car has been designed to be as good as it could be, not just to fill a gap in the market."
Bass-wise, Prefer it slightly heavier on the sub-bass (really deep < 30-50 Hz sub-bass) since our ears aren't as sensitive to it, but starting to balance off after that. That's just me though. 
