I have the large screen without Nav and a smartphone. The Sync turn-by-turn directions provides an arrow and distance to the next turn on the center display and on the large screen. With the smartphone Sync app you can get directions sent to the car, but you can only use it while the car is not moving (GPS in the phone with the app on locks your phone until you stop).
On Mapquest you can send a destination point to the car through your smartphone and that works well also. It's up to your personal preference. Sometimes I wish I had a map on the screen to see the roads around me, but then again it would probably be a bigger distraction. I don't see a wrong choice.
Stock with factory Sony 10-speaker HD stereo and 4-wheel disc brakes.