Your comments got me thinking, so I read the manual and sure enough it says that AAC formats can be read. The I-tunes default AAC works at 256 kbps and this can't be played on my concert stereo even though it names the track (Appears greyed out). I did a bit of experimenting and tried it at 192 kbps and it played the tracks fine. Also worked for 128 kbps but not for 320 kbps. I can only therefore suppose that my player will not support bit rates over 192 for the AAC format used in itunes(I haven't tried 224 yet). Maybe it is different if you have the symphony sound system or the B+O. Has anybody else had similar findings?I'm pretty sure that my itunes rips to .m4a which the car will play.
I did discover over the weekend that it does not appear to support .wma lossless - supports .wma but not lossless - bit of a bugger as all of my music is in lossless format. I've elected to go with 320 kbps .mp3 which is all but lossless quality. It's a quick and painless job to convert using something like dbpoweramp batch converter.
Another point I picked up on was that the car does not support the NTFS file system for those of you planning to use a portable hard disc. The hard disc needs to be formatted FAT32 - which most are by default.
Tried an ipod Touch (latest firmware), SD card and portable HDD and the HDD seems to have a very much quicker response time than the former two.