Thank you. Yes to me it feels very much an upgrade, compared to the Fiio Q7, which I have been using as DAC/HPA driving the HD800's (original).
Imho it is not a matter of more bass, treble or mids, but classical chamber music sounds more natural, at first it seemed a tiny bit less detailed, but it also feels a bit less nervous and more enjoyable. Electronic music can bring very nice euphoria like Boris Brejcha - Vienna
on Qobuz.
It could be that the Q7 is not the best match for my phones, the DX9 turned out to be a very good match. I can now listen continuously album after album and more and no listening fatigue at all.
With most modern television sets you can change the picture sharpness, setting it too high it can give the impression of more details but it can also become exaggerated and unnatural. That also seems the case a bit with the Q7. But if you have less unforgiving phones then the Q7 might be a very good match.
The DX9 is so transparant, it makes my phones sounding even more as if they are electrostats with good grip on the low notes. The review
on Soundnews is spot-on I think, also when music has to sound raw, it will do so. Very happy with this investment into my listening pleasure