To possibly answer your question:
Most likely your car is sirius ready if it's an '03+. From one of the message boards I learned that you can (with the radio on) press and hold the "m" button for 20 seconds and up will come a serial number. Then press the "+" button and a software code will appear. IF the last two digits are 50 or higher than your car is sirius ready. That means that you can use the data cable and power cable in teh trunk (same one you would use for the cd player) and you've got a plug and play install. You just need to hook up the antenna. And by the way you can also connect the sirius tuner box to the bmw cd changer if you want (it shares the same prewire then back to the headunit).
84110141981
E46 E39 E53
Sirius Receiver
Requires install kit - antenna - etc. List: $ 299.00
Sale: $ 239.95
Steps:
1) Fish out CD change cabling from left side trunk
2) Connect Sirius antenna to Sirius receiver
3) Connect Sirius to CD changer cabling in trunk (3 & 6 pin)
4) Swap head unit as required
5) Power on
6) Activate Sirius via Internet
Parts on the cheap:
OEM Sirius BMW receiver (discount via Circle BMW)
Terk antenna (cheaper than OEM BMW via Best Buy)
MY 2003 head unit
Info on BMW/Sirius joint venture:
http://66.246.14.172/phpBB/viewtopic.php?t...er=asc&start=15