Upgrading the memory is incredibly expensive and bulky! The 32mb "backpack" (which does include rechargeable battery) runs about $79.00, with the 64mb @ $119.00.
I love this player except for the backpack situation. If this unit used flash/smart/mmc etc. I would say it is the best buy around. I still think it's great, but be ready to pay some big bucks if you want an extensive music library with you and have some place to store the goofy backpack (be careful-the prongs on the battery hook-up bend easily causing the unit to not work!).