Take a look at rtorrent.
It can be configured to look at a "drop" directory (even a remote one) and automatically download torrents.
Just save the .torrent files there and wait for the file to arrive.
It also has the advantage that the machine it runs on does not need any Desktop Environment (KDE / XFce, etc) - it is completely text-interfaced.
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You can find a SlackBuild script
here.
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