So some guy does a crappy job converting some files by using low quality MP3 and it's MP3's fault? That's like saying that all hamburgers are bad because you got a crappy one at a dirty diner using crappy meat!
MP3 at 256 to 320kbs is pretty much indistinguishable from a CD. There isn't any "reverb" or "slapback" on any of my MP3 conversions. I remember when I first put MP3s on my RCA Lyra player. I tried using 64k because Compact Flash card were pretty expensive. At 64K, the sound was pretty lousy. 128K was decent and if you were just listening on the cheap earbuds, you really couldn't tell much.
For a car, CD quality is pretty much a waste. Unless you're blasting the sound, the noise floor is way too high to really hear a difference.