I just got my 2-pin balanced cable for my CIEMs today, so I'll be able to say where I notice a significant difference in sound quality vs single-ended with those. Not going to to get MMCX balanced cable for the IT03s, since I won't keep them, and my son doesn't have a balanced source (the iBassos are a gift).
I'll post later tonight or tomorrow.
Interesting results. I could hear differences, but pretty subtle ones. With both CIEMs the sound-stage got just a bit larger.
With the C5s, imaging became even more defined (location of instruments more specific.) Also,
maybe the bass is raised up a bit in the mix.
With the AS2s, the bass got even a bit clearer (when a bass drum or tom-tom strike and a bass note overlap, each is more distinct).
Less dramatic differences with the Opus -- I could probably be convinced that it's the placebo effect, especially since the changes I hear are similar to those from the DP-X1. Of course, you shouldn't discount the possibility that the cable change, not switching to balanced that causes some/all of the perceived differences.
If anything, I'd say you should expect results which are similar to what I had with the C5s if you move the IT-03 from single-ended to balanced.
Reading this, I realize it's probably completely un-helpful. Sorry