Thanks to you for that wonderful link! You may want to try monitoring the
http://www.bimmer.org/x5/messages/ board -- a bunch of crazies, and a very active board. There is not a problem these guys haven't seen. They have great meets as well!
I really enjoyed my 4.4 X5. It was everything I wanted in a vehicle. The M5 is close, but not quite as functional -- more on the all-out performance side. The 4.6 still retains much of the functionality, but definitely leans ( or should I say flat out is) on the side of performance. Enjoy that beast!