Hardware arrived this weekend. Geforce 6200 AGP. Had to dremel off a little bit of the lower part of the bracket for mounting in the dell dimension 4100 because it has some stupid guide things on the bottom of the slots. The original GeForce 2 MX had a small chunk missing there (only it looked like it was made that way) so I just shaved down a similar part to match on the new card.
Impressions so far is that Beryl runs a lot smoother, and the front-end software for MythTV looks a little snappier. Came with S-video TV Output, so the hooking it directly to the TV will have to wait for a while until I get a new AV receiver.
HDTV Tuner card should be in tomorrow or the next day. Looking forward to trying this whole MythTV thing out in its entire glory once I get that working.
I will update then.