Personally, I have two large repositories of data.
1) My media center, which holds recorded TV and my ripped DVD images. 300 GB, 320 GB, 500 GB, JBOD mode (redundancy is not necessary).
2) My server, which handles AD, DNS, web, etc. Two 36 GB RAID 1, four 500 GB RAID 5 with an option for six more disk or infiniband. Power usage is around 200W, mostly in the disks (the box, sans drives, pulls under 50W). Uses a 6 tape DDS-4 autoloader for backup, and all other machines can and do back up to it.
Personally, have you looked into a WHS?