thanks raps.
ideally what i was looking for was software recommendations people used to sync/make off-site backups to a nas box as opposed to storing at cloud level. i'm sure it's not fool-proof, but one big advantage i've read about backing up this way is that the limits on storage are determined only by the amount of space available in the nas, but obviously there's a hefty investment in boxes, drives and your time. otherwise as you say anything cloud based that runs beyond the terabyte can be pretty crippling