I'd also have a backup if funds allow. Do you really fancy ripping all those discs again......
Ok Bob I have the choice of going for a 2bay enclosure or 4 bay the difference in price is about £30 would it be better for me to go for the 4 bay and get smaller hard drives and get the extra hard drives as i go along lets say 2TB each which gives me a total of 8TB which I do not think I need more than that What do you think? is that the safer way to do itI don't think it's actually a NAS as it doesn't seem to have a network connection, it's just a RAID enclosure.
Regardless of whether it is or not I don't think I'd bother about mirroring a 2 disk array and just have an external drive as backup.
I would agree 4TB is a bit on the small side and probably go for a 6TB drive. I'd also recommend a WD Red.
EDIT - Chaz replied at the same time as me.
I'd still go for the WD Red as although it's not a NAS it's an enclosure with more than one drive, so you'll still have some of the benefits of using the Red such as vibration reduction and cooler running when other drives are in close proximity.