In any case, I now have a very nice web front-end to SageTV with an especially nice (customizeable) show schedule interface.
Notes and screenshots here.
Next up, I want to play with SlimServer. For some reason they say that it doesn't work with the MediaMVP interface for SageTV, but it's supposed to work with the MVPMC firmware. I have hopes. Mebbe I'll have to come up with a way to select which firmware the MVP loads.