1. Well this is going to sound dumb, but i'm really out of the loop these days. What all applications does bluetooth have, for a car stereo? I thought bluetooth was just a little IR signal for those little earpieces for cell phones. How could that be useful with a head unit?
2. As for the USB inputs, the only useful thing I can come up with for those would be like, if you put your whole song library on s USB flash drive, (that was large enough to hold it of course) and the head unit could read them from it and play them out through the speakers. Is this why they have usb inputs these days?