Minimum reasonable system requirements for Windows 7 Media Center

Minimum reasonable system requirements for Windows 7 Media Center

I'm looking at getting a Windows 7 Media Center box to replace my current MythTV box. I travel a lot and my wife doesn't like the maintenance required for Myth. Although in the past, I've built my own machines, it seems to make more sense to go with something small, low power, and quiet (as opposed to the giant Antec case for the MythTV box).