the shuffle does sound the best of the ipods...but the ibooks don't sound very good, either.
of the ipods with screen, the 4G ipod's DAC is considered the best-sounding (the wolfson DACs in the 4G and 5G are different).
here are some ways you can make your ipod sound better:
1. rip your CDs at better bitrates. Apple Lossless sounds better than AAC/mp3, and higher bitrate mp3/AAC are better than lower. also, you might want to use something like LAME for even better mp3 encoding. better headphones like your e4c will reveal bad rips and poor quality encodings...
2. use the dock's line out connected to a headphone amplifier for even better sound than using the headphone out. you can read more about headphone amplifiers at
http://www.head-fi.org...sorry about your wallet.
good luck.