My Recommendation would be look at the marine market, the one in our ski boat works really well surprisingly, I believe it's a Clarion. Plus you gain some water resistance. In the jeep I use my LG pro ear buds, but even w that if going up a hill people have a hard time, but that is partially due to my new exhaust tip being 2" shorter then the body (keep meaning to fix that lol). I pretty much use the ear buds in all our vehicles, I don't like it in my wifes Armada, or my new ram 5500, to me they are ok, but not as clear as the LG, only car we have that is good is the vette, but summer only tires and an exhaust that goes into stealth mode probably play a big role in that.
I must say I'm surprised by Jerry's BMW though.....