just to contribute and help gain perspective on cd quality VS mp3 quality:
the mp3 format was made to shrink the size of audio files while retaining decent quality. it´s mainly focused on reducing the size, though.
logically, the only way to shrink the file size like that, is to degrade the audio quality. an uncompressed audio file is around 40 MB in size. the average mp3 is 1/10 of that size, at around 4 MB.
so if you take away 9/10 of the information, you can only imagine that the quality is much poorer, right?
the difference is in the small details. it´s just like the JPG image format, or poorly compressed video files. a shitty compression will leave you with a blobby mess.
the lower frequencies suffer. the mid range frequencies lose their fine grained nature and either get smoothed over or get a coarser grain, and the higher frequencies suffer the same but alot harder. cymbals end up sounding like this weird fluttering whistle-type noise, and lose their timbre and presence. it just sorta gets washed out and blended into the wall of noise.
in a perfect world, all digital audio would be expanded from the typical 20Hz-20KHz range to a more natural 10Hz-40KHz range, and the standard for audio files would be raw and uncompressed. i would want an ipod with as much storage capacity as possible so i could have room for the 10 times larger audio files, and i´d listen with a top-of-the-line monitoring headset. that´s my idea of a good night!
edit: which is also my idea of how i want to listen to Ki