Anyone been using the Maxx for GPS in the car? I have read of issues with heat in the old Razr Maxx when using the GPS for extended periods or having the phone plugged into a car charger. Any experience with the new Maxx? Also, is the speaker sufficiently loud to listen to nav or a podcast without routing through car speakers? Not concerned about music fidelity or anything like that. Just speaking volume while in-car. Thanks!