How much data are we talking about? I get confused. Is it 1.5TB or is it 2.5TB?
Then, how backed up do you want to be? Think about if you REALLY need daily backups. While Raid might be cool and flashy; if you don't need it you don't need it and running it only creates cost.
If you have about 2 TB of data then i would just buy 3 external HDD of 2TB size and replace them every 5 Years. Then rotate them around every time you do a backup. Can you automate your backups? Not to the point of you not having to do anything. Unless you choose to pay for 2 cloud storage providers and both offer you to save your backups in an unchangeable state.