It could've been that they planned for AUX functionality in the future and it would have been cheaper to start producing the same hardware right away (no change in manufacturing process), even though it wasn't implemented in software yet. Perhaps.
BTW, I was in a similar situation few years ago... Decided to buy a used HU with a newer SW version from a fellow fanatic. But in my case, I was replacing a tape-cassette HU too, so I got a newer HU plus a CD player, so it was a no-brain-er. In your case, you might see whether it would be worth getting a HU and using the AUX cable vs getting a CD changer compatible converter.
Last edited by The Jiveman; 12-27-2012 at 10:57 AM.