I didn't click on the links (yet) but what I've heard is that there will be XBMC set top box coming out in the future based on the Sigma SoC. In that respect it won't be a build-your-own type of device, it will be a finished product. We'll have to see how they finish polishing up the interface, as I didn't like what I last saw running on a desktop.
_________________________
Bruno
Twisted Melon : Fine Mac OS Software