I fully understand what you are saying! Even with sync3, the best navigation i can get is the phone Navi screen cabled into the Sync3 screen. Just the map display. The audio turn by turn is still pumped out of the smartphone speaker.
I might have some issues with my beat up phone that is preventing me from getting the audio through the speakers. So, I am not going to give up until I get the next new phone in late July.