The CD500 has an auxiliary input, but I don't think either of them can control the Ipod remotely like most "Ipod interfaces". You'd be controlling songs directly from the Ipod.
Thanks for the additional info. I would like to be able to play from an ipod in my car, even though I do not have one yet. I don't plan on playing any MP3 cd's, so i'm trying to figure out whether to spend the additional money for a Nak CD 500.
It seems as though the only advantage that the CD 500 has over the CD 400 is the ability to play MP3. Are there any other advantages that I am not aware of?