Another option you might consider is MP-2 instead of MP-3. The downside is you only get half the compression (gee, imagine only 250 hours of music on line instead of 500) but the upside is that it is entirely lossless. I work at a radio station (4 stations, actually) where all of the music is on hard drives encoded MP-2. There is difference between the original and the encoded musc. If sound quality is your primary consideration (it is just about my ONLY consideration!) MP-2 might be the way to go. The folks at empeg have told me that their unit will be able to play back MP3 and MP2 files indiscriminately - you can mix and match them with no problems. So you can put all your Rock & Roll (and other children's music ;-) on MP3, and put the good stuff (Mozart, Bach, etc.) on MP-2.

"There Ain't No Such Thing As A Free Lunch"