I've had the P77MP in my car for a while now and am very pleased with the
performance.

What I'd now like to do is to be able to have a multi-CD changer but still
use MP3 CDRs. Is this possible with this headunit?

Pioneer don't seem to do any MP3 CD Changers, but I'm not sure whether I
need one or not. I know the headunit has the IP Bus system and I wondered
whether this link just provides control to the external device or whether it
transmits data as well. So if I just bought one of Pioneer's CD Changers
would I be able to put MP3 discs in it and it would just read the data and
let the headunit do the conversion?

I guess the other option would be to have an MP3 CD Changer from a different
manufacturer and an adapter to plug into the Pioneer - but would I still be
able to use MP3 discs in the changer?

Any help would be much appreciated.
Thanks.