I don't know anything about the car's sound system, but aptX is a pretty common Bluetooth audio codec for music and these days it can run up to 420kbit/s with the adaptive codec, or 576kbit/s with HD, 24 bit at 44.1-96kHZ, so it's not unreasonable to think you could hear the difference between high and low quality audio sources with that (since even high quality compressed audio tends to be less than 420kbit/s)