theres a company that will allow you to remove the old tape decks in the 2300/2500/4000's and have them put in a 30pin Ipod dock which will also respond via Beo4 using the I believe the A.Aux commands..... it's really a great idea, extremely cool, but very pricey. If you look on the forum you'll find the site that offers the conversion.
BV7-40 MKIV, BeoVision Avant 32, BeoVision 8-32, BeoLab Penta MKIII, BeoLab 6000 x 3, BeoSound 9000 MKIII, BeoLab 7-4, BeoSound 4000, BeoPort, BeoVox S45-2, ML/MCL Convertors, A8's & Form 2's.