I recently purchased the portable, mobile vehicle kit, Star Mate 7 w/remote.
Even though I only have the stock system in Park Ave, the sound quality is very good using the cassette adapter.
It can transmit onto a per-programmed FM station but the sound quality is best with an AUX in (which stock radio does not have) or "better" with cassette adapter.
This works well as I can move it from one set of wheels to another easily.
Kinda messy with cables and such (no substitute for an in dash set up though) the kit came with a magnetic antenna that should be placed on roof, but with the wide deep dash of PA it actually works ok on Velcro inside windshield too.
Antenna wire not connected in this photo. Was just setting it up from other vehicle at time of this picture. Using supplied good quality suction cup below mirror, it also comes with vent clips too for base mount.
Link about star mate 7: