I now have 3x3TB drives inside of the Server instelf, 2x5 Bay Tower Enclosures each with 5x2TB drives and 2x3TB USB drives which are all "Pooled". That means currently there is 35TB of which 13TB is used and 13TB is a "duplicate" thereby leaving 9TB free (although really only 4.5TB due to duplication). Expansion capacity is huge as I can just keep adding drive tower enclosures.
I used to do something very similar - maintain a large power-sucking NAS computer with a bunch of RAID'ed hard disks. I am very much over that now.
I now just have a single 2TB bus-powered drive connected to my Mac Mini. This is more than enough to keep a decent amount of movies and music locally. Everything else is in the Cloud - NetFlix streaming gets a lot more viewing in my household than my locally stored content.
All my local media is backed up to the Cloud as well - thanks to CrashPlan unlimited storage plan. So I don't even bother with RAID enclosures or local backup.
My setup is very simple, lightweight and easy on the power bill.