I have an older Pioneer XM box (non-Nav unit) that has an wired display that goes up front, it has an FM modulator built into it, I can't think of the exact model, but it does have the ip bus connection on it for sure, I think it was the 900 or 903 or something like that. Does anyone know if that unit can be plugged into the D3?

Yes it can, but you won't get the channel logos. I think you will have to buy the bus cable also

Perfect, good to know, thanks!

I'm pretty sure that the 903FM(or close to that model#) will only display 8 chars of text.