Torrents would be particularly well suited to this type of thing. Unfortunately I set up a very similar archive for something else, it never took off because people just couldn't grasp how BitTorrent works. We caught a load of flak from people who had just heard of BT being bashed in the mainstream press for being the root of piracy and didn't understand how it worked.
Anywho, regardless of that failure, if you are interested, I will have a dig around for our code - it has all the usual stuff you'd expect (categories, comments etc.) as well as auto-seeding, virus scanning and torrent creation from files.
Also, there is this huge misconception that WordPress is just for blogs. This is so very wrong! It is an extremely flexible CMS platform, and you'll find that many high-traffic sites actually use it.