Advice please on back up

Hey all wonder if i may ask for some help please. I currently got a 6tb WD RED PRO for my HTPC for my plex server which i run on my HTPC in our bedroom and use that as our plex server for the Pi 3 via Rasplex. Just wondering what the best software is to back up my Movies and music. I know on site and off site is the best way to back up Data so i will be getting a 6TB external so i can back up to that on site what is a decent software for off site i have seen Crashburn is suppose to be decent. Not sure how good as im not currently using anything at all to back up when i should be doing really

This one has been mentioned on here a while back and looked good value to me. Personally I don't like that it doesn't have a private encryption key to do the encrypting locally prior to transmitting the data but that doesn't seem so important for movies and music.

https://www.dupplica.com/

Crashplan is another alternative if you have another PC at a different site that you can trust.

Dupplica looks good.