I would like to build a new computer to be used as a DVR and media server. I am thinking of using mythtv as the DVR software, but short of that decision I am completely open to suggestions.

Requirements:

1. Must be cheap.
2. Must have low power consumption (since it will always be on).
3. Should be quiet.
4. Should be small.

I'm really not sure where to start with this project, and am open to any hardware/software suggestions. Is it possible to build a small quiet and cheap system?

*Keep in mind I am working on this project because I am tired of Cable rate increases, but I can't imagine living without a DVR so cost is very important and I would like the system to be sub $200.00. The system also needs to handle the new digital broadcast system.

Thanks for the help,