entire NAV/Command Center? I'm thinking about buying a 2003 BMW 745i. I'd like to add some subwoofers and possibly and auxilarry audio input to the existing NAV and stereo system. Is it possible to make any such changes without completely ditching the original system?

It seems like everything operates through the iDrive, is it possible to maintain this system (which seems like you almost have to in order for the car to function properly), while making some minor upgrades?

Check this out.
http://www.bavariansoundwerks.com/prototypevehicles.php

i dont think so coz its all registered to the car's computer!! so :S

it's not worth the cost or effort these cars are at best computers on wheels and you are asking for trouble if you go into the wiring or try to change anything thats not sold by BMW