setting amp gains?

I just hooked up my pair of pro 80's and they sound great with my sony bean style mp3 player. which is what I used to when tunning. I made sure to zero out everything on the clarion cmd 4 head unit and the mp3 eq's. I popped in a cd yesterday for the first time and it was very distorted with the volume set at 23. when I play music on my mp3 player the speakers are clear with the volume set at 27/28 which is 3/4 of max the head unit will play. which is where I tunned them at? my question is is there a disk you can buy to help tune a system? and does anybody have any good links to a step by step process on how to properly tune your system? also when setting up the pro 80's I should run the amp at full and not high pass right? I search the boards and couldn't really find anything thanks in advanced.

You will never be able to tune your system to play both an MP3 player and a cd. The bitrate of the recorded music is so different, MP3's are compressed and this is the difference in sound your hearing. You'll just have to keep the volume down more when playing cd's. I'm sure someone else can explain in scientific detail way better than I.