I recently upgraded my system (300A o/c'd to 504Mhz) to a PIII and CUSL2 and was inspired by the article in (I think?) NOV's Maximum PC.
Since my old parts are still very useful I needed something to do with them.
After I find a good case (black/small/preferably a desktop), I'm going to build up a system using an ATI All in Wonder Pro (16MB AGP) card and any 5.1 sound card (leaning toward the Phillips 'Acoustic Edge').
I'll then split off my cable from behind my TV to the video card and route it back to my receiver.
I'll also network this PC to the on in my Den (the upgraded one) and I'll be able to share files and play games between PC's. Also, I'll have front USB ports for game controller access and an IR keyboard so I can teach my wife to search the net in a window while watching TV.
Just sounds like an awesome way to make use of what was once a great system.
Check out maximumpc.com . Maybe the articles are up about it.
Now I am really desperate for a desktop style black ATX or AT case.
Get the smallest desktop ATX case you can find, then go to Wal-Mart and get some vinyl upholstry dye from the Automotive dept. Use Acetone to quickly wipe the residue from the case. Take all the covers out and spray everything separately. Viola, the same method HP used to make my color-matched cd-rom I had a few years ago!
Didn't see anything on maximumpc.com. From your description, I'm still unclear as to how you're going to use this machine as a Tivo box...
As to the cases, I thought you were looking for a (non-PC) case, suitable for an audio/video component. But I still may be able to help... A few weeks ago, I ran across a couple of sights that reviewed tons of different cases and had links to case manufacturers' websites. I'll see if I can find it in my history.