Yes, I've adjusted volume but calls still come in low. I have to raise volume to 30 for adequate volume.Have you adjusted the Bluetooth volume through the setup menu on the stereo? I have mine set on "14" and incoming calls are nice and audible. Before I turned it up, it was set at "10" and some calls were hard to hear.
I have the iPhone 5, it sounds good with that.
Come to think of it, my friend's galaxy s3 didn't sound so great in my car. Maybe I didn't turn up the volume completely. Don't remember.