Hi Jofm5,
Not sure if your post entirely relates to SD's or not, but in case the latter part relates to mine; as mentioned I already have an eSATA approach that I take semi-offsite*, but I want to use ethernet-over-mains and a NAS as a more convenient alternative. Within reason (and my 50Mbps is fine), performance is a non-issue.
If your post does relate to SD's, then ignore the above!
*The fully off-site part of the strategy involves two 500GB USB HDDs that are swapped on rotation.