Im currently working on a project to do this very thing. What I am doing is setting up a network(since I need to get my ps2 online anyway) and Im going to put a second PC out by my HT.
I have 80% of a pc already(just need a case for it

) and Im going to pick up a vid card with TV-out. This way the PC will be hooked up to my tv so I can select songs, and all my media will be on my main PC in another room.
The reason I am doing this is mainly because I dont want to run a 50ft rca cable to my HT and I would rather invest my money in this rather than a mega cd changer. The added bonus is I will have my ps2 finally set up online, and I will be able to sit on my couch and have access to all my music(I plan on ripping most of my cd collection to wma) and be able to play it on my HT.
This probably more than you are looking for but I'll let you know how it turns out if you want.
Here is the list of equipment...
Router
Network cable
2nd PC with network card, tv-out vid card, and decent sound card.
Cables to connect to HT(and possibly a ground loop isolater if their is any 'hum' in the sound)
Its actually turning out to be fairly cheap, the most expensive aspects are the video card and router(which I already had anyway) the rest is less than 40 bucks CDN.