Although I use on-ear headphones with my iPhone now, I used to use (and still have) Etymotics hf5 IEMs. These don't have artificial bass enhancement so are actually accurate monitors, although with some songs you may wish they had more bass. However, for vocals they are fantastic. The other use they have is blocking out external noise - I think they block out something like 26 decibels so are better than noise cancelling headphones and better than earplugs!