I have a machine that I intend to use as a disk server/backing-up server. (It is already being used for this but needs upgrading/tweaking)

Current Setup:
It has 1 40 GB disk that has the OS (F 10) installed on it. I then have 2 1TB drives that are setup as RAID 1 (Mirrored). I think that it is setup as software raid (It has been a while since I set it up). I believe that the motherboard has firmware/driver RAID.

I have now ran out of space on this and need to add more drives. I intend to add 2 1.5 TB drives.

The question is: how should I go about setting this up? Should I use software/OS RAID or try and let the motherboard handle it? My intention was to keep the 40 GB drive as a '/' partition and then use a 160GB drive as a '/home' partition. I then wanted to use the 2 1TB drives as a RAID 1 partition and then use the 2 1.5TB drives as separate RAID 1 partition. Does this sound like a good idea? ANy suggestions on how to do this or links to good tutorials?