yeah i've seen pictures of a ety4 gutted, same driver their hearing aids use.
poke around on the web, you should find a lot.
i'm a EE not a historian/theology teacher.....dont know much about the holy grail...sorry.
though a flat sound waveform can be desired, it depends on many factors as to what is "better",
like bellsprout said, every one has a preference.
on that note.
if you look at the waveform of 600+ custom IEM's they all have a heavily mechanically (porting/tuning/audio-acoustic filters) altered sound.
a flat waveform is typically desired if you are in a audiolab where you have access to hardware equalizers, amplifiers, monitoring software/hardware,waveform dividers,psychoacoustic editors.
with them you can listen to your "raw" PCM audio and modulate/edit it to your liking.
back to the subject of the thread,
if you are listening to from your small portable media player, id recommend something with a low impedance.
if they are active headphones for you, make sure they will fitwell, and (i recommend) a replaceable cable.
UE,westone,JBL,ETY,v-moda...theirs alot of them.
stay away from shure...there lower cost headphones are dreadful.
a good place to shop.
http://www.earphonesolutions.com/