Well, my Mythbuntu backend CPU just bit the dust and I've decided to use the opportunity to upgrade to a smaller and, with luck, lower-wattage machine (the currently-nonfunctional system was drawing 50w but only did SD). I've read the hardware wiki but I couldn't quite get a sense of the smallest/lowest-wattage system that was likely to avoid configuration annoyances and be able to support 720p playback so I thought I'd ask here. Does anyone have hardware suggestions (or hardware to definitely avoid) for the following requirements:

For a Mythbuntu 10.10 backend where record will be via a HD-PVR
Smallest form factor possible
Supporting 720p playback either via CPU or GPU (but this may affect the form factor issue)
Lowest wattage possible
Highest-possible Mythbuntu hardware compatibility out of the box

I'm hoping for suggestions on CPU, GPU if necessary for VDPAU, plus motherboard if suggestions aren't for a SFF combined CPU/motherboard.

Thank you very much for any suggestions!