For Canada in the 335i, Nav is a $4500 option and it includes Harmon/Kardon and a backup camera.
My wife's IS250 has a reverse camera and i never use it when I reverse. But the backup camera in the BMW has the lines superimposed and I used it when parking during my test drive and it worked awesome. BUt i have been driving my whole life without that stuff and I have gotten by.
Nav in this car is sick...it finds restaurants and stuff. But in the IS250, I rarely use navigation. 90% of the places most people drive are familiar to them.
Not having the stereo hurts a bit, and since I drive a car with a Mark Levinson system, it will be noticeable...but I think that the voice of reason and the $4500 is telling me I can do without that stuff.