I built an MP3 player, used a PIC18F4620, and if I remember right I used up practically all of the onchip ram in one word variable:
sectorbuffer var word[1536], or maybe it was more than one. I'll check when I get home tonight.

Easiest way is to just write the program and compile it. If you get an error, you can't.
Wish I had more instant info for ya....
JDG