Let me tell you, all car CD player do NOT play CD-R's.
I went through 3 before i got one that did. I started with a high-end Panasonic (high-end for panasonic), then a stupidly expensive Alpine, and finally ended up with Eclipse.
Some Alpine's do, and some don't. The one I tried, we installed it at the shop without testing it because they didn't have one hooked up. Other alpines played my cd's okay, so we figured it would work. It didn't. I mean, it played some, but there were glitches and excessive skipping.
Anyway, you should have absolute no problem with CDR's with a deck designed to play mp3's.