i keep all my mp3s on a very large external hard drive, and i move it around among various machines.
you can build yourself one cheap with an enclosure:
http://www.newegg.com/Product/Produc...losure&Ntk=all
my "mp3 player" is an old laptop jacked to the stereo. i plug the external drive and it's done.
sure it's not portable but i've never been convinced by the price of portable mp3 players except for an iriver (flash-based) i bought years ago. i still move files in & out of it, for the day, or trips, or whatever, and i carry an interchangeable ton of mp3s in my laptop...
so hm whatever you get it's a good idea to keep a separate repository of your dearest files.