Howdy - an ex-Roadtreker here - posted frequently when I had my 190 Versatile - showed pics of the laptop pedestal(s) that I built for the R/T (and my F 150 too), upon which I secured my laptop and ran my MS S&T for GPS. Worked great (still does for the F 150) but for my new "ride" the laptop either sits on the pax seat when I'm driving alone, or on the lap of my Wife when she's along - not a good deal !
I absolutely refused to get one of the portable GPS units - the display, for me, is too small - so, I've recently (like 2 days ago) had an Alpine 1 DIN head unit installed to replace my OEM BMW radio. The 1 DIN fits into the "slot" that the old radio used to occupy and has a 7" flip-out screen. I opted to get the GPS, Sirius radio, iPhone docking add-ons. The head unit comes with DVD/CD player, AM/FM radio.
This is an excellent set-up and I highly recommend it for others who have the "Baby Bear" idea about GPS (not too big, not too small but just right)
I would have gotten the 2 DIN unit (stays exposed when "off") but I would have had to relocate either my HVAC or my MID unit (multi-info-display - onboard computer) and done some fabrication. I'm getting the 2 DIN for my Wife's vehicle however - it'll fit in without fabrication or moving anything.