The answer is simple, you MUST convert your tunes to MP3 in order to use them in beoplayer. Not AAC. I would delete those duplicates you have and convert the originals to MP3.If ALL of your music has been bought from the itunes store you may not be able to convert them for use as MP3.
Out of curiosity, What kbps bit rate is the music encoded at? And which beolabs are you using? If the bit rate is around 128, you may be sorely disappointed about the sound quality. I've heard 128kbps music on my lab1's before and it's a sound worthy of sea-sickness.
“Quality is never an accident; it is always the result of intelligent effort.”
Your health and well-being comes first and fore-most.