I didn't see this method mentioned anywhere, and it's pretty easy to use. Instead of setting up some kind of automatic ftp uploader for your torrent files to the seedbox watch directory, you can just install a Chrome extension or Firefox addon!
In Chrome's extension store, search for Remote Torrent Adder. Set it up for your seedbox. When you click on a torrent download link or magnet link the torrent is sent directly to your seedbox! So simple.
One quirk, the default settings cause a big PITA on this website since ".torrent" is caught as a torrent download link so any link you click on from "www.torrent-invites.com" it tries to be sent to the seedbox!
For Firefox, you can use ruTorrent WebUI for the same kind of function. The addon is pretty young and in more recent versions of Firefox you have to log in to the seedbox every time you add a torrent. Perhaps that will be fixed at some point.
Hope this helps someone out there!