Don't know if anyone caught in sharansnl's review, but the X7i has a BA driver, not dynamic. That would account for the clear, balanced sound (pun intended).
Interesting that, given the rounder shape of the body (compared to the barrel shape of the X10i, which does not have BA driver). Must be something about ceramic material that it works best with that type shape, similar to other ceramic body IEMs recently. (Meelec CC51P, etc.)