Sorry yes, I would certainly not go down the route of linking in to the iDrive, if you want an inbuilt unit then it would have to be the BMW unit. I disagree about satnav affecting market resale values, it is a well known fact that in the UK, options add much less value to the resale value of a car than the purchase price of those options. You should spec a car for what you want, not what the person who gets it after you might want!!