The low-power Intel parts are interesting, but I don't think I'd jump just yet (if one could wait) for a build-it-yourself system. As someone pointed out in the comments, one could get a MacMini for what he paid (and newer/faster ones are likely coming in the not too distant future).
I haven't kept up with all the features and limitations of all these various media center/home server/streaming interface boxes. The idea still intrigues me, so I'll look into it again when I've got some free time (Ha!).
Thanks for the pointer.
Cheers,
Scott.
(Who never did finish his MythTV project...)