Why not just mount them both in different locations?
So you have 2 x 160GB
You could have one as your main /home folder and the other as a Multimedia folder.
So, your home would could like:
But then you could have your other disk mounted at MultiMedia. Which would have videos, pictures, and music.
$ ls /home/<user>
Documents Downloads Desktop builds scripts MultiMedia
That way, you run no risks of a RAID 2 setup and all it takes is a simple backup and edit of fstab.
I see no reason that this is not a good alternative. Is there a reason you NEED a 320GB partition?