Looks ilke a 16 port? What model is that? I am running a 24 port ARC-1280ML at home, but my friend's ARC-1220 died a horrible death, taking the raid array with it, so many sure you still backup and don't rely on RAID. By the way, you may want to concider running RAID6 from the get go..would only give you less then 6GB formatted from your 4 3TB drives though. Also, Areca doesn't do so well with desktop drives...so be warned. I am assuming you will be running SAS>4xSATA cables on this puppy.
EDIT: See the model number on the card now on the box