Just skimmed over your thread here so apologies if I missed too much.
I am using a zotac zbox nano for the size at this stage as I want it to go in my dash. It however has a HDMI output and a displayport which I believe can be used to daisy chain monitors. Might be an option for driving multiple monitors.. It also uses and AMD e350 chip which is low power but still quite a lot of grunt..