The ZX2 has seperate ground giving many of the benefits of balanced. The new players apparently still have seperate ground on the 3,5 mm and full balanced on the 4,4 mm. No user replaceable battery on any of them though
It's been reported that on these new daps you can access both internal storage and microSD at the same time when connected to a computer.
I intend to use JH13 and Signature Pro just as I do now with ZX2