Look, I get the drive for change, I really do… but here are my 2 cents.
For my brain and ears, the ZX507 is better than the Cayin RU7 which has been heralded as an excellent dongle…
It has better synergy with headphones such as the power-hungry Sennheiser HD660S2 than my RU7, despite having half the power…
It's also faster than my WM1AM2…
And you already have one
Again, I do get the drive for change, I really, really, do — but every time I do the DAP merry go round, I land back on Sony… so, my advise, if you move on from the ZX507, get the ZX707, WM1AM2 or WM1ZM2. But, if, like me, you didn't get the ZX707 due to it's form factor because, let's be honest, the ZX300/507 form-factor is just
— keep your ZX507.