Linux is installed (first Arch (boots really quickly), but then Debian, as I am simply used to it).
Finally I got a SqueezeBox software renderer running on the box. So now I am able to use the Pi to play my music stored on a cheap NAS through my quite old stereo. The trick: the official Logitech Squeezebox App for IPhone is now my Rasperry Pi remote. No need for a display/TV!
As I have a really bad terrestrial radio reception in my house I can now use the Pi to play a huge number of internet radios. Again controlled by the IPhone.
I was waiting for ages for a cheap solution of this problem.