Got BMW factory Sirius installed in my 2005 X5 4.4 with NAV and 6CD. It was a struggle. Local BMW techs couldn't figure out why the Sirius RX was degrading the sound of the CD 6 changer. The CD sounded like crap after they installed the Sirius but after 5 days and numerous calls to BMW tech support they figured out to swap out the 6CD changer. Why I don't know since it's only 6 months old but that's what they did and it works fine now. I'll have to change the antenna from the magnetic roof mount to inside the wing but that's another project. Overall very happy with Sirius. Lots of choices. I agree with most other reviewers that sound quality is about 80% of a CD but way better than FM. Of course it varies greatly on the original recording. Controls are very nice through the NAV but BMW missed the mark not having advanced features like Artist and Song search or the ability to rewind the song in progress.