I have been auditioning CIEMs since getting the NT6pros some years ago and have been shocked at how well these compare to the other TOTL CIEMs. Keep in mind that I am comparing my custom fitting CIEMs to universal demos that is not really fair, but I have yet to hear any that beat the pros. In fact, compared to the TOTL HPs, the Pros often scale further with a great source. For example, in my opinion, the pros best the HD800 and the HEK when paired with the Ygg/Rok stack. That says a lot about a CIEM's SQ.
In recent comparisons, I find that the competition is getting closer, but not better. At a certain level, you are not getting better SQ, just different tunings that you may prefer over another. For example, are you a Abyss or a 009 fan - both in the exotic range but with very different tunings. What I am finding is that to match or come close to the NT6pro SQ, you are comparing to something in the $2K plus range compared to 1200 for the pro. Some comparables that I have heard lately are the Zeus-R, A12 Adel, k12, Harmony 8.2 and other large name TOTL CIEMs, but none beat the pro - just different tunings. If I could only have one, it would be the pro. If I could have two, then I would get a different tuning for different moods.
Now if only I can get these guys at Hidition to answer my emails as I am not lucky enough to be local to them nor speak Korean. My pro had a pin break off in my socket and need to get the socket replaced. I am going crazy without them functioning. Please tell Hidition next time you are in the shop to answer the email from the crazy guy in Seattle with the broken socket.