If you buy your stuff from Tischer BMW, you will have to specify each individual part you need-- I am not aware of any pre-defined kits. If you order from BimmerNav, they can help you put together a kit for your car. I am not sure if BimmerNav identifies everything on their web site, but they can certainly get it. If you were to fashion an "official" BMW Sirius kit for your car, these would be the current parts (except for the radio) that you would need:

65.12-0 416 377 Sirius receiver
65.20-0 034 887 BMW Sirius antenna
84.11-0 141 976 Installation kit
84.11-0 141 977 Audio extension cable
84.11-0 141 978 CD Changer "audio Y cable"

It does matter which BM53 radio you get. The oldest part number that will work is PN 65.12-6 927 911. And, the newest BM53 radios can work with a new CD changer to fully support MP3 CDs. The BM53 PN 65.12-6 988 276 is the remanufactured version of PN 65.12-6 988 275. The two are effectively identical, except the remanufactured version comes with a $500 core charge. The -275 version of the radio is more ($485, I think), but it does not have the core charge. Tischer BMW has the -275 radio, but it does not show up on their online site because of the way that the parts catalog is organized. You can request the -275 radio if you email them or specify it in your comments.

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2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input