Network Backup Solution Out of the Box?

file terminator writes: I want to buy a network drive for home usage, and am looking for something that would allow for secure and encrypted remote backups over the Internet to a second network drive, preferably advanced enough that all drive content does not have to be transmitted every time. The solution may come as a pair of network drives, and two-way synching would actually be a plus. The drives would be behind respective NATs and setup must allow connecting to any target port. The solution should be readily available (no obscure/local brands/solutions) and not unreasonably expensive. Does anyone have any recommendations for a full out of the box solution?