Is there a difference in sound quality of different Bluetooth protocols or standards? I asked my son if he'd like a Bluetooth to RCA adapter for his car rather than using the AUX cable. He said he would like one. I read a review of one on Amazon and a reviewer wrote something like, "it's only Bluetooth 3.0..." and mentioned he didn't notice any sound quality issues and that it was fine for him. So then it got me wondering if there is some limitation of older Bluetooth standards.