With your budget:

1. Sansa Fuze+ 16GB w/ a microSD card for the expansion slot.


2. Creative Zen X-Fi Style (available in either white or black)


Have no experience with either of these current units, though I do have the earlier Fuze (no +) and it worked fairly well and the original X-Fi (worked decently). Both should be compatible w/ m4a files (my units are).

For a little more the 32GB Zune becomes available to you. I really like mine, though after a couple of years of consistent use the battery is starting to go on it.