gxavier38 :
Also, what if I didn't use RAID?
If the homeserver is only backing up files that are already stored on other computers then its not necessary, though the more redundancy you have the better. If you are storing files on there, you should have some kind of backup solution in place (whether its RAID or just a program that backs up the files to another drive).
If you only want 2TB of storage you can probably get away with using MOBO RAID. Id suggest reading up on the different types of RAID and see what you really want.
For a simple set up you can just have 2x2TB 7200rpm drives in RAID 1 (thats one usable drive and one backup), if you buy a new MOBO you should be able to have SSD cache drive that will speed up the access of common files and OS. Also look into RAID 1+0 and 0+1 for redundancy and speed.
The one negative about RAID is (as far as I remember) you cant add any more drives into the array, unless your using JBOD which isn't really RAID.