I'd look at the Shure SE125's, Hi-fi man RE-400's, Klipsch Image X10's, TF10's
I don't really like the S4's, they have good clarity for a mainstream $80 earphone and really deep bass but they are annoying in the 7-8khs range I think? I can only listen to the for a while with guitars without eq. The SE215's aren't perfect, I like them a lot better but they are smoother and less agressive and a little to rolled off up top. Never heard the RE-400's.