Buy a bluetooth kit and install it yourself. I put one in my previous '04 and it worked great. No dealer recoding needed. You will have to give up the BMW Assist though unless you buy a combo unit from an '05+ model. I never used the Assist, so it was no big deal for me. There is a great write up on the X5 World home page that shows you how to do the install.

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'06 X5 4.8is, TiAg/black, cold weather pkg., comfort seats
'07 750Li, TiAg/black, sport pkg.
'05 Ford F350 silver met./slate gray, Lariat, 6.0 PSD, CC, DRW, FX4