But I'm not too concerned (well, at all really:-) about the e46. I would like to be able to fit a CD player behind the nav screen in my e53 X5. When looking for a car I'm sure I saw this combo. I remembered it as the dealer was surprised, saying he'd never seen it before.

IIRC it's a DIN sized hole back there, what happens if a Business CD player is pushed into it?