If the cost of the BMW system is an issue I'd recommend looking at Becker's Cascade 7944 - latest version of the TrafficPro - as an alternative.

This doesn't have a map display but does show graphical representations of junctions on the radio display. In every other respect this is a very good alternative to the BMW system, matching each feature apart from the large screen. I recently retrofitted one to a Boxster and am very impressed with it's performance.

http://www.caraudiodiscount.com/acat...avigation.html

http://www.becker.de/beckerCC21/www_...sp?language=En

BMW factory fit:
Prof Sat Nav £1800
Bluetooth £500
IPOD £150
DSP £???
Voice Rec £250


Cascade:
7944 £550 (imported from Germany)
Becker IPOD kit £60

includes Sat Nav, BT, DSP, Dymamic TMC, MP3, Euro "maps", VR, option for audible warning of cameras, perfect integration with Radio and CD, POI + external custom POI. Cascade has much better language support and will speak out TMC messages as they are received.

"Map data" is held on a dedicated CF card.