heres a 16gb microsdhc for $15 if you dont mind the mail in rebate and going to frys to pick up, also its a PNY, not an HP card like the link says http://www.frys.com/product/6561523?
SDHC Class VI and Class X will work faster with the Pandora. Buy a good brand and go for the faster speed, you'll get better performance with a card that works as spec'd.