I am not quite sure how to play this reply so I will just go for it.
Most consumer electronics are "little more" than specialist computers these days (many even run linux of one form or another which means you have a point to work from). Some of the lower power embedded stuff is more than powerful enough to pull off a lot of things a PC might regularly do which has given rise to a lot of hacks (TVs are getting the treatment these days) but for a while now routers have been a prime target as you seem to have discovered which extends to having nice things like torrent clients running.
Torrent is an interesting protocol not least of all because it is fairly demanding of a network system (200 odd simultaneous connections is never fun)- things can be updated like that and mesh networks exist but straight up end user style torrents do not really happen on that (especially not if you want nice options). This means no official developer will really ever bother with it especially when the "torrent is just for pirates" line still just about works. The demands of torrent can also trouble lesser routers (I am sure we have seen routers fall over when you do not dial back the amount of connections) which is one of the reasons why I suggested you consider something else.
X86 and windows is awful for this embedded game (power, resources, cost....) so you will probably have to play in some other world. Should you ignore the command line and config nonsense when reading up the first time around then it is all quite simple and stuff you have probably done for years- install OS (one does come installed), install programs, run programs (these plugs are squarely aimed at the somewhat savvy consumer and as such have just about everything is download and run type format unlike most hacks).
You can build small windows boxes using atom boards and the like but they are quite expensive vs the cheaper stuff like we are talking about here. Likewise there are various clients for embedded systems (looking at the likes of mediatanks) but those things come at a hefty price- those "plugs" are about as cheap as things get unless you want to buy a dead battery laptop and use that (laptops do not make that good 24/7 servers mind).
That stuff probably does not concern you all that much as that is over with after you have it set up. What you are likely thinking more about is what happens once I get there. To that I answer there are clients with HTTP frontends (indeed there are for most "downloader" type protocols) which I sense is what you are looking for- you stick a torrent in a given directory (or send it by a form or something) and it will open it and start downloading give or take what is said in the config files, to check up on it and maybe tweak a few things all you do is dial up the server (probably as an IP address on your network).
It will ultimately look something like
http://www.transmissionbt.com/images/scree...lutch-Large.jpg
Site with a client
http://www.transmissionbt.com/
There are hundreds of guides and a search with sheevaplug and transmission should drag up a bunch. The wiki at the intial site has a lot of stuff worth reading though
http://plugcomputer.org/plugwiki/index.php?title=Main_Page