I have only one recommendation regarding a RAID array (should you decide to get one):

COOL THOSE DRIVES.

When someone stacks several high-speed 3.5" disk drives in a PC case, they don't often realize how much heat they put out. You need air circulation around the drives because they'll heat each other up and the drives can fry if you're not careful. They even make little replacement 5" drive-bay cover plates that have little fans in them. If you don't have air going around the drives already, I'd recommend at least one of these faceplate-thingys on the middle of the three drives.