[mythtv-users] How hard is it to build an HD MythTV?

[stefan_jones at comcast.net]

Related question:

If you have a frontend / backend system, with a front end servicing a HD, you are obviously going to need a relatively stout processor in the front end. Or a middling processor and card with good MPEG2 offload capabilities. 

But what about the back end? It will be doing HD capture, which I understand isn't all that CPU intensive. But where does the commercial flagging / transcoding get done?

This is relevant to me because I'm trying to decide whether to go for a new combined system, or to retire my current box to be back end only, and make a new HD-capable frontend in a trim little box.