If you need multiple cards, I would have one 16GB card
Oh yeah, thought I'd let people know I got a reaaallly fast, Class 10 Sandisk 32GB MicroSDHC (UHS) on Amazon for around ~$23 and it arrived today, works perfectly with my DS2 so I assume it'll work for my GW -- pretty good deal for the best kind of SDHC. Was able to write a 2GB ROM (DKCR) in around 2 minutes.