Purchased Monster DNA In-ear for Xperia SP
To me Xperia SP audio output is too under powered. (power saving purpose maybe?)
Ending up getting an ipod touch 5th gen for music.
For casual phone chats, I uses my old Bose mobile iphone earbuds. (don't remember the model)
Found the model.
Bose MIE2i mobile headset
I would say if one really wants to listen to music with their phones, get a portable amp. FIIO ROCKY E02i is pretty good.
then pair it with a decent earphone.
I personally stopped using portable amp, because of the cables... just look too awkward.