The power converter was from the dealer. It is like $10. They also sell them on ebay...

The Ground Loop Isolator I got from Radio Shack. Please let me know if you need part numbers.

Matt's correct.

Both XM and Sirius are compatible with the X3, the XM Direct kit is compatible with non-Navigation models only. Regardless, we can get satellite radio integrated like if it was offered from factory.

I have the same problem. My Sirus and Ipod both cause the AUX input to "disappear" after a few minutes. My Ipod without the power connected works fine. My dealer says that BMW is aware of the problem and "they are working on it". Not too optomistic as my X3 is a 2004. If they haven't found a solution by know, looks like they aren't looking too hard.

A Ground-Loop Isolator may be required when the auxiliary device is charged/power from the vehicle's 12V battery source. This part can be found at Radio Shack (Cat.No. 270-054) and will eliminate unwanted noise caused by ground loops.

I installed the ground loop isolator and the problem went away. Most particularly you will notice the fidelity improvement and no more hum. The "Aux" is now working properly even with a powered device such as XM Mifi, iPod, xM2Go, etc. plugged into 12v source.