I've got a WD Caviar Green drive I'd like to put in a hardware RAID 1 array for a home server (for storing music, photos, etc). Problem is, the specific model I have isn't shipping any more. Will I be okay pairing it with a newer model, specifically if the newer version has a larger cache (64MB compared to 32MB)?
Yes - this might even be a good idea - least according to this SF question, since you'd have different failure rates between the disks. Your system is probably not aware of the larger cache at raid level, and the system should work at least as well as if you had two 32 mb cached disks.