In my opinion, mids are everything. Good solid bass and treble are just the assistants to the mids. The Shure SE535 IEM's for example pretty much are all mids, with a nice lower end, and a treble cutoff and that IEM has a cult following these days.
If you want a mid-centric headphone
HD-650 (going to be rather warm, still works for rock for guitar distortion)
Those are all roughly around $300-400 and I could roll a dice and be happy with all of those for their own reason.
Grados have a hot treble (LOVE IT) and rich fuzzy mids, with sort of a sharp bass signature. Bass drum and snare both register as snaps instead of thuds/booms. Thats what they mean by fast bass.