If you want expandability, why not go for a TRGPro or Handera 330? (Both made by TRG). The TRGPro is basically a Palm III-alike with a CF-card slot -- you can put any CF flash memory card you like in it, and I know from experience it'll take a 256Mb card. The Handera 330 is a slightly larger successor with a 240x320 grayscale display, CF card slot, and IIRC an SD slot. (Never played with one, but the owners rave about them.) Both are battery powered (not rechargable) and as TRG stopped making 'em earlier this year they're available for a song on places like eBay.