Purchase MP3 to WAV converter ?

look for the wavepad sound editor. There's a pro and a free version. You can even edit music, compress it, etc. I think you're missing some serious sound quality by listening to only mp3 but that's another conversation! If you have a good car system, listen to a well recorded piece of music on cd or some of the new hi rez downloads available from places like hdtracks. Night and day, I think you'll be impressed.

My cars, going back to '06 or '07 have all been able to play MP3 files.

MP3 is fine in the car. Sorry, CD only, so you are up against a 650 meg limit.

If your car player won't play an MP3, maybe an upgrade, plug in player would work?

Just download several of the free ones. If you are having such great success with most MP3s you hopefully will find some that work on the few that are troublesome.

The tech is changing so quickly I would not spend money on a converter. A free one that works 100% of the time may be right around the corner.

I cannot suggest what to use as I do not like MP3s. I have had great results with EAC, Dbpa, Media Monkey and JRiver (all free versions)

Good Listening to you!