Also have E5 which I think does do much help sonically apart from increasing the volume some notches, What I really feel lacking somewhat in M2 is a wide soundstage. I think its too closed and not at all airy. So what I am looking next is some earphones which would be as fun as M2 (may be better on high end) with a wide soundstage. That is what my next hunt is.
Great Stuff!! Seriously, I mean that is some feat, bought a Brainwavz M2 (never knew it even existed before I saw head-fi) and it is just awweesome (not that I have many other to compare) but I think its just what I wanted!! Thank you for making this as easy as reading!! What do you think would be next step?? (I cant believe I am already thinking this!!).
Go slow - if M2 satisfies you for the time being, stay with it.
Think about what you exactly need - M2 + a few things more / less? Something totally different from M2? Then hunt for it.