I honestly don't think what I get from my ES3X has anything to do with the "right signature" befitting to your preconceived liking. To me they are clearly technically better, sound right, more convincing, mainly having greater extension along the whole freq range. I don't think within high-end customs there's anything like what my ears heard from the SM3, SE530, 535 & CK10, at least from a technical standpoint.
If I didn't know the UM3X, to a lesser extent the W3 and more recently the IE8, and only knew the other IEMs listed in my sig, I would never have said that (high-end) customs were overrated, ie I'd probably have said "If you can afford them, try to get them. They are worth the price difference, even if obviously not two/ three times better"
To these ears the ES3X is significantly better SQ-wise than the SE530, SE535, SM3 & CK10 and therefore, definitely worth the upgrade. For me, though, as great as the W3 was, it became fatiguing too soon (after an hour or so), ie quite impressive & exciting for shorter listening sessions only. I think, for example, I might get a similar reaction from the UE11 Pro (but only guessing).
These days both UM3X & IE8 come with detachable cables and I still think that for most people seeking excellent EQ these two universals are a better choice than getting high-end customs. And, like I said over a year ago, $300 - $400 is already A LOT of money. But, from memory - and hopefully I'll be able to confirm this shortly - the UM3X was an even better (technically) IEM than the IE8.
