You can use 32gb cards in the Droid 2 if you wanted. Pretty much any MicroSD card out there should be fine but I would at least look for a decent transfer rate, usually you'll find users posting their results in reviews such as on Newegg.com. You can't always go by the class rating as the actual transfer rates can vary wildy. But the class rating is a decent place to start. I'm currently looking at a class 4 Patriot card that is really very highly on Newegg and that many have excellent transfer rates with. For example, there's a class 6 card on there that is reviewed as having awful transfer speeds.