I had a Bose in my Mazda, and surprise surprise it skipped like a kangaroo on speed!
I knew I was selling it so I bought some decent quality blank cassettes and taped some CD's... it took me back a few years I can tell you
The quality was actually really good so I would imagine if you hard wired an Aux in to the tape player you would get a pretty good quality sound, certainly better than those FM transmitter things....
The digital radio ones make me laugh, crystal clear digital signal, then FM transmit it to your head unit