did some testing with CD-RW meanwhile (TDK 4x-12x highspeed, Sony cd-rw700hs, Verbatim 8-12x)
I was able to burn audio CD's via Itunes perfectly with the mentioned blank CD's. (Sony took ages but works...)
Well, I've bought more than 300 songs at the I-Tunes store. I guess as long as I have to use Itunes for
saving the files on CD I'll stop buying.