Thanks for your thorough reply!
Yes, I read about the Nationite S:Flo2 and that it has great sound quality, but the UI ist supposedly pretty aweful. That, and the fact that it seems hard to obtain at my location, kept me from considering it further. The Ipod touch is nice, but too big for me, as I'm allready carring a huge HTC One X with me. I also don't want to pay the additional fees for the video and fancy stuff, which I would never use.
Regarding the Hifiman & co, I am just not willing to sacrifice that much usability for sound quality. On the go, I'm maybe listening for max one hour a day, so it's just not worth it to me, considering that I have a quality setup at home.
After digging through walls of opinions, I came close to ordering the latest Ipod Classic 160gb, intending to rockbox it. I don't want to be doctrined by apple, but I liked the pod for it's big screen, providing additional rockbox comfort. I like that it gives you plenty of space and good sound quality. But then again, it would cost me 300$ including case, not even having a touch interface. Anyway, the last days when I was using my HTC with poweramp, I realised that I might not be willing to sacrifice touch controls and fast accessible features like playlist and searching after all. As a source, it certainly isn't great, but I think the DT1350 really makes it acceptable on it's own. So for the moment, at least, I think I will stick to my smartphone, but will be keeping a look out for any newcomers in the future. The only downside is the lack of remote controls. Having to unlock the screen for every command is really tireing.