If you're getting a TE with the nav preparation, bite the bullet and get the BMW nav, as its fully controllable with the wheel on the handlebars. Aftermarket ones won't work with the wheel.
Essential protection extras, for me, are:
Fender extender AND Mudsling
Radiator guards
Frame guards
And you can sell a kidney and fit the full Akra system, tinted screen, HP levers; the list goes on!