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).

I've been looking at the Dell Inspiron Zino HD, which is a new machine from Dell that is their competitor to the Mac Mini. At the low end it comes with a single core athlon, which is too 2004 for me, so I'm looking at either the 1.5GHz Athlon x2 x3250e or the 1.8GHz Athlon Neo x2 6850. My understanding is that both of these processors are designed to be very low power and fairly efficient, but which one is enough for the purpose.

Will the 1.5GHz still work well for playing back 1080i HDTV and whatever streaming we decide to do? At the moment I'm not planning on going BluRay -- but will it handle that? Will this Dual Core chip be fine other Windows 7 Media Center stuff? It won't be used for anything else, just recording TV (HdHomerun), watching TV, playing movies, etc.

The Dell Zino HD with its ATI Radeon HD3200 should be well able to playback 1080i&p HD content, the processor is certainly nothing to be worried about.