Sounds like the mystery may be coming to an end !

Circlebmw have very competitive pricing with their Sirius Receivers ... so you might want to check that out for your new receiver. The latest sirius receiver 65 12 0 398 140 will work with both NAV and Non-Nav cars.

You should have no prob selling your current receiver .... just make sure folks know it compatible with the in-dash CD player only (from 10/2002) and it will work with certainly E46, E53, and E39)