My choice:
MEE Pinnacle P1.
Review
https://www.head-fi.org/showcase/me...adphones-with-detachable-cables.21283/reviews
I feel the same as you toward all audio, I don't want fun or exaggerated, I want it to sound neutral, no V or U shape signature. MEE Pinnacle P1 will give you neutral... deep accurate bass with no excess boom boom and crystal clear highs with no ear fatigue causing sibilance.
These IEMs also have exceptional soundstage and very accurate detail.
Comparisons:
Etymotics (can't remember which model) have crystal clear highs and also have other outstanding audio qualities except they have absolutely no bass, I don't mean that the bass is pulled-back, I mean they have very little bass reproduction (yes I have tried different tips to make sure there was proper isolation). Also, these IEMs are very uncomfortable for me due to the extra deep insertion needed.
Westone UM Pro 50 have the opposite problem of the Etymotics. These have great bass extension with super detailed bass, no excess bass, great mid-range, but the treble is terribly laid-back with some detail and no sparkle. The soundstage is huge and these are the most comfortable IEMs. The lack of treble detail can be helped with the use of EQ.
Sony MH1. There was nothing I liked about these, sonic signature not neutral, dull sounding, and lack of soundstage.