I have a 2003 E46 and would like to install the new Sirius Satellite radio. The dealer is quoting me US$800 installed. The receiver is $299, the antenna is $125 the installation kit is $25 and if you have a 6 disk changer installed you need an additional splitter cable for $15. The question I have is that I have one of those shark fin antenas factory installed from BMW. No one at my dealership really knows what it is for. Some speculate that it is for the BMW telephone and some say it is for the Satelitte radio, and some say it is just the radio antenna. I do not know if I need to spend the additional $125 for the satelitte antenna when I think I have it already? Does any one know? My dealer has only installed one of the units in a X5 and they said they put the satelitte antenna inside; which goes against everything I have read about needing the antena on top of the vehicle.