Jeff, Mine is a 2001 X5 3.0i, non-dsp. I did swap out the door pillar tweeters and add a sub and amp in the trunk.

The fm modulator in mine sounds pretty good, no interference issues. The sound using the modulator is better than any fm station, but not nearly as sharp as my cd changer. So I did experiment and here's how I got MUCH better sound out of it:

I have an in-dash cassette, which obviously is not used these days. It did, however, prove to be quite useful. I decided to try a cassette adapter from the line out jack (3.5mm) on the back of the docking station. First I tried a Monster iplay cassette adapter. I don't know if it was faulty, but the sound quality was quite poor and the squeaking of the wheels on the cassette tape was noticeable. I returned it (Best Buy) and decided to give it one more try. I bought a Sony cassette adapter (for a Walkman) and tried the same thing. Success! The sound quality is much better than with the modulator-much sharper and picks up the bass better and absolutely no wheel noise! All for 20 bucks at Best Buy.

The nice thing about this setup is that I keep the cassette in at all times, and when I want to listen to satellite radio, I simply switch my stereo to "tape". Since the cassette unit is covered, all wires are hidden and tucked behind the wood flap covering the tape deck and by the s50. In short, the install from the cabin looks exactly as it does in the pictures above. The location of the unit works out perfectly to hide wires neatly, and is also in a great position for the driver to see and access.

In all, I'm very happy with the s50 and don't know if I'd pay all the bucks on a factory satellite radio on a new car. I'd probably do this same install, although I'd use the aux input jack on a newer model.

Good luck.