The WD Caviar Black drives are awesome in my experience. Solid, reliable and they really are faster than normal drives provided they aren't super full.
As for the RAID options, I would personally do a 3-drive RAID-1 for the protection. Three reasons - using software RAID (i.e. OSX's built-in RAID tools) results in less performance than a dedicated RAID card will deliver, and RAID 0 with less than 4 drives doesn't tend to be worth the price in my experience. The third point is that the more drives you add to the RAID, the higher the likelihood of failure. Minimal performance boost and greatly increased risk of losing all your files doesn't exactly sound worth it to me. If you want to fill your bays and get more storage space, configuring RAID-1 may be a better option.
The ideal RAID system starts with a dedicated card (even a cheaper one), 5 or more drives and a RAID 5 configuration. That's where you start to see performance increases that justify the expense AND enjoy safety with your precious files.