I'm doing the aux install this weekend with the above post as guidance.

I bought my cable here: BMW E53 X5 Auxiliary Audio Input Cable 3.0 4.0 NW:eBay Motors (item 190342634723 end time Nov-16-09 16:45:15 PST)

Only reason I'm pimping this seller is I bought the wrong cable (I have nav and bought the non-nav input due to my stupidity/not reading the listing) and he let me exchange no problem which is pretty cool since I made the mistake. The install looks pretty easy.

Joe
2006 4.4