I have a chance to try out the ZX1 today at Sony press event in my country.
The UI is very fluid although it runs on very old Texas Instrument SoC with 1 GB RAM. I plugged in my MDR-EX800ST and listen the same Nora Jones's song as the one in Ginza and other songs in it.
I think the sound signature is like F800 I'm using but with more bass and detail. The stage is also a little wider than my F800. Compare to Fiio X3 which I used to listen. X3 has slightly more bass than ZX1. Mid is also thicker but both of them have less detail than ZX1.
ZX1 sound meets my expectation. Now I'm going to save money and buy it when it will be released around next February.
More is not necessarily better in this case. The DX50 also has more bass output than my F807, but it does not go quite as low. I prefer bass notes to be as natural as possible and not accentuate likes most DAPs & Headphones out there. Thanks for your impression.