A 128 MB player will hold only about 2 CDs. At the 10 to 1 ratio you would need 20 x 60 MB = 1200 MB or 1.2 Gig to store 20 CDs. The little solid state MP3 players don't have the capacity you are looking for.
You can store 10 CDs on a CDR and play it back on a portable cd player that supports MP3. The indexing is really bad though.
Any of the high capacity MP3 players with a hard drive would give you the capacity you are looking for and more. An archos jukebox with 6 GB or an Ipod with 5 GB would give you space for about 100 CDs.
Or to get it back onto topic of this board you could put in a 20 GB hard drive and a motherboard and build your own jukebox. I assume though that you were looking at small portable units.
Bob