Also, does anyone have any suggestions for handling large amounts of data? It's been recommended that I get redundant backup with a RAID device, but not a NAS device because the second operating system (NAS) will potentially add jitter to the playback?
RAID comes in many flavors but the consumer in general uses raid 1, mirroring.
One disk is an exact copy of the other so if one fails you still have all of your data on the other drive.
This is an excellent way to protect you against losing your music collection due to hard disk failure but it won't protects you against dropping the unit (kids, cats, dogs, drunk), water, fire, theft.
It won't protect you against user errors like deleting the wrong files or applying the wrong tags. Sounds logical but I have the feeling that a lot of people think they are safe because they have a RAID system.
As far as user errors are concerned, the difference between RAID and a single HD is that with RAID all your user errors are stored redundant.
RAID is NOT a backup