This is more directed at the back end of things. The Fileserver, and the DVD ripping/encoding portion of things
The nice thing about fileservers, is that you really don't need a lot of horsepower (depending on how smart the gear is you're streaming to)
If it's another pc, you could use something like a p2 350, with 128 mb of ram and be VERY successful.
Currently I'm experimenting with 2 different fileservers.
The first is just an old PC that I've upgraded bit by bit. It's now a celeron 2.6 Ghz(free cpu!) with 1.5 gb of pc 133 ram (all free stuff too)
I've got 3x 300gb hard drives in it, and currently have about 750ish gb of movies/mp3/pictures.
I use this machine to serve all the files, as well as to do my Video encoding. I use dvd decrypter to rip the movies (this software has since be squashed by SOme compaNY) to a video stream, and then autoGK to encode it to a high quality DivX movie
with this machine, it generally takes about 4 hours from the time I put the DVD into the drive, to the time I can watch the movie on my HTPC (or laptop, or prismiq, or Lyra)
I'm also fiddling with a NSLU2. it's a linksys box, about half the size of a normal broadband router, that accepts USB hard drive enclosures, or just USB flash drives. It's nice because it uses about 1/10th of the power of a fileserver, and is completely silent, with no moving parts.
It's also hackable ala the wrt54g's, so lots of development and 3rd party applications are available for it. I'm undecided if I'm going to use it as a fileserver, or if I'm going to just stick a 4 gb flash drive on it, and use it as a small webserver, or just potentially to use it as a repository for all my network backups (ghost images)
For the fileserver, the standard build is xp pro, running Ghost, Teamspeak, mysql, php, a phpBB forum, and streaming software for the prismiq, and MRTG to monitor the rest of the network for congestion