Anyway, for $10-20 you can get any ol' used car stereo from a junk yard that'll work and have a 3.5mm aux port. You can even find some with USB and grab a dirt cheap 32GB nub/stick from Microcenter or wherever.
After the initial setup, it'll be easier and cheaper in the long run than buying CDs. Less wasteful, too. Plus, nobody's gonna see a CD booklet and think they might be valuable and break into your car. Assuming you keep them in there.
I've even seen USB stick mini booklets if you wanna load a bunch up with FLACs if your car system can tell the difference while cruisin'...