I use CrashPlan to achieve a similar result. I highly recommend you try it.

CrashPlan will backup to your network (free), your friends (free), your external drives (free), and optionally to their servers (paid) all in parallel. Anywhere you install their software you can share a backup volume/folder and it is automatically visible to your other crashplan installs as a backup destination. On top of that you can use your own encryption key, so the data is protected even in case of a subpoena to the backup servers.