I just added this to the NT6 Pro thread:
Update to my early impressions: After 10 more hours of listening, all weirdness is gone leaving nothing but goodness. The full sound spectrum blends effortlessly and naturally. The way I would describe the signature now is full fidelity. Although it is described as extended at both ends, I see it as capable of effortlessly playing the full spectrum while the competition is truncated sounding small. The music sounds as if it is coming from full sized humans in the same room with me rather than coming from shrunken humans the size of ants. In addition, all instruments and voices are scaled naturally and correctly and 3D sounding as if they are in the same room standing around me. The competition often puts the drummer or and the singer in another room down the hall with the door shut and in the worse case, the whole band. This is very close to the experience of listening to my large Maggies with all their planer goodness paired with dual M&K subwoofers through a dedicated Rotel 1000 watt amp.
As for brightness, I don't see how this is a bright CIEM - this was my biggest holdup in choosing the NT6 Pro after reading the reviews. It feels clear and natural and is in no way fatiguing. However, the rumble and definition in the bass notes are what call the most attention to itself as exceptional. Normally, bass this good covers up the detail rather than adding to the detail. In this case, I can clearly hear the different resonance characteristics coming from the singers voice, the bass guitar, the lead guitar, and a flat bass kick from the drummer. These are usually muddied up into a single bloated bass note.
Although the NT6 Pro makes every source sound its best, it definitely scales well through the lower tier sources. Going from the iPhone/iPod to the Sansa family (Clip+/Zip/Fuse) there is a clear improvement moving to a much clearer cleaner presentation that is much fuller and more resolving. Moving up to a Colorfly C3 / C&C BH2 combo, the presentation again becomes even cleaner clearer and more resolving with a bigger more dynamic sound and fuller bass note. I hate to say it, but there is likely to be a ibasso DX100 or R10 in my future.
I am very happy with my choice and all my fears were for not. I don't like bright presentations as I find them irratating - I don't find the NT6 Pro bright or sibilant but rather well balanced and clear. I don't like dark presentations as I find them lacking in detail or bass bloated - the NT6 is the clearest most transparent thing I have heard yet. I usually don't like what is considered balanced as they are usually missing both ends of the sound spectrum taking me to a bright (lack of bass) or boring presentation - the NT6 Pro is very balanced but extended to include the full spectrum at both ends creating a very exciting presentation. I still want a SE 5-Way, but I feel it will be complementry rather than competitive in sound signature.