Not my personal experience, but I was talking to a guy at the last AutoX who likes to have his go pro (same as yours) mounted on the roof , kinda where the some light is, and he uses his iPhone 5 for Audio. Said he liked te sound better from the iPhone but it may also be because the go pro is way in the center of the car.
You can a microphone set up pretty easily and move it around for if you want more engine, exhaust, or tire sound.
