I don't have much advice to offer for Myth, but if you want a bit torrent client to be on the box, I would recommend TorrentFlux-B4RT strongly. It by default, can do RSS feeds of torrents. It's entirely web based. It uses bitornado for the actual torrenting. You pick a range of ports and you can run one torrent for each port. You can submit .torrent files by their url, or upload them on the web interface.
Try it out at http://TorrentFlux-b4rt.bcrook.com with the username and password "kclugdemo". (I will be deleting that temp account in a week.)
I also have a shell script if anyone's interested, that you can use to add a torrent to the queue from the cli. Install doesn't take much longer than half an hour. I would however, recommend doing the torrenting from a public facing host, and rsyncing to the myth box, or mounting the torrent downloads directory from the myth box if your network is fast enough.