Thanks and servus!
I wote them a mail, let's see what they have to say. hifi-forum is a place I visit daily, so I'll definitely be checking there, as well as Meizume, Head-Fi and all other forums I frequent
But as you say yourself, I'd rather buy a new one than a used one with low battery life. I have that myself, although my battery is still pretty good for 3 years' daily use.
I have heard that the handling on the S:Flo can be tricky, along with battery life, plus it's quite big for mobile use. So I'm still a bit hesitant about that one.
The ZEN looks good, and I actually like the buttons. Makes it easier to operate the player in the pocket of my jacket (even though, with a bit of experience it works with the M6 as well).
And btw, Mods, please feel free to move these posts if they are too off-topic (which they probably are, sorry)