Looking for advice on a network drive

I’m planning on hooking up an external drive to my Airport Extreme as my Infuse server. I’ve got an extra 3 TB Hitachi Desktar 7k3000 drive I’ve been using as a backup for all my media files, and would like to just get an enclosure for it, to save some cash. But all the enclosures I’ve been finding on Amazon and NewEgg seem to have a pretty major negative, whether it be only USB 2 or SATA 2 support, or being plastic (which doesn’t dissipate heat well) and crappy, or being too expensive. Does anybody have a particular favorite enclosure that they’ve used for something like this before, that is fairly cheap? ($30 max, $20 or less would be nice)