Does your university have a backup solution you can make use of? The one I work at lets researchers onto their Tivoli system for the cost of the tapes. I think I've got somewhere in the neighborhood of 100TB on the system and ended up being the driving force behind a migration from LTO-2 to LTO-4 this summer. If you are going to go and role your own and use disks, I'd recommend something with ZFS - you can make a snapshot after every backup so you can do point in time restores.
Also, I'd recommend more capacity on backup than you have now to allow versioning. I was the admin for a university film production recently (currently off at I believe Technicolor being put to IMAX) and I've lost track of the number of times I had to dig yesterday's or last week's version off of tape because someone made a mistake that was uncorrectable.