Hey there bit late to the party, since I already sold my M9 for a Z1R, but here are my quick thoughts.
I listened on the ZX300 and was wowed with how well the M9 presented male vocals. There was a warmth that didn't rob too much clarity, and they were presented quite forward which is a contrast from many high end sets that have a very recessed lower midrange. High pitched female vocals I felt didn't cut through enough, with a more relaxing tone that doesn't demand your attention like they should. Lower pitched female vocals benefit from the warmth and thickness that male vocalists did. Elvis, Billy Joel, and Shankar Mahadevan sounded great on these. Ariana Grande and the Weeknd, not quite as great.
Bass is pretty good for a BA set, but sounds a bit flabby, not as fast as I'd like for the amount of impact provided. Texture is very good, but it leaves the impression of being hollow but boomy, which is a pretty odd feeling.
The treble on these is extended but not piercing, you don't get the "shine" you do with other sets, but I think that works well with the slightly warmer than neutral signature.
Soundstage is of average width, but the imaging and separation is top notch. You can pinpoint singers and instruments really easily if you have a good recording.
Overall I found these to be a really great set for relaxed listening, often my choice for late nights. However, I didn't find any category where they stood out as the absolute best. They're just... Very good at everything, which makes them slightly boring (compared to other high end IEMs obviously). For that reason I sold them and went for the Z1R which are very confident in what they are: bass cannons with good tuning.