Cool avatar ...
Noise cancelling? Check (better than most). Portability? Check (smaller and lighter than most).
I find the ER6i's to be fairly versatile (except I don't listen to rap -- but on some electronic music with massively loud bass, the ER6i's do manage to convey a significant *audible* bass ... but they might not be what you're used to, espcially at first), but as stated above, they are detailed and most certainly not in-ear sub-woofers. It is easiest for me (and most comfortable, if that's an issue for you) to get a great seal by using foamies -- the Shure black foamies fit the ER6i's and last a lot longer than other brands currently offered. Also, I think the highs are toned down a bit when using foamies. I've worn them for four hours at a time and found them to be non-fatiguing sonically and physically when using foamies ... a bit less so with flanges.
The fit and sound signature took me some getting used to (I went from ER6's to Shure E3's and then "back" to Ety with the Er6i's). The foamies made all the difference for me (of course, your mileage may vary, but the small Shure or Comply foams on the ER6i's fit very well and sound very nice for me).
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Phones (in order of purchase):
Sony MDR71, Sony MDR51, Etymotic ER6, Panasonic RP-HJ50, Shure E3C, Koss
PortaPro 2, Creative EP630, Etymotic ER6i, Sennheiser PX-100, Sennheiser HD555, Future Sonics Atrio M5