Can ONLY go on past (unfavorable) experience...
Had a couple of different FM/tuner connectors for our iPods in my wife's VW Jetta....... Bad quality sound, no matter what we tried...... different stations / volume / etc. Always had poor quality 'reception'.... Now, that may have just been the car's radio, but it sounded great when not iPod connected. And right now I can't tell you what they were but I suspect at least one was a Belkin setup and I'm not sure of the other. Also this was some time ago, so newer, more current equipment may be miles different in quality... but also I know that "most" newer auto come with an input jack that you can connect your iPod via... (again "most", but not all).
Sorry I can't help with the selection/referral process... just giving on person's experience.
Bob K. rnkiii