Hello. Thank to a fellow poster, I found a place to pick up changer adapters for those who already have a CD changer.
The person I spoke with on the phone was very courteous. With regard to the I-bus , AI-bus issue, you can check your car stereo manual around page 17 and it should say which one you have. I happen to have a AI-bus for my HK CD-deck on my 1999 323i. I don't know if all E46 are AI bus, they may be... Unfortunately discountcarstereo did not have an adapter for AI bus although they had one for the I bus. However, they told me they are expecting them sometime this month. I'll keep you posted.