Get the Gigabyte 780g motherboard, no video card needed as the integreted graphics plays 1080p HDMI, go read the reviews about it, it's the best HTPC motherboard yet, and its VERY cheap.
Newegg.ca - GIGABYTE GA-MA78GM-S2H AM2+/AM2 AMD 780G HDMI Micro ATX AMD Motherboard - AMD Motherboards
There are Asus versions of it and other brands but I do believe the Gigabyte one is the best out of them.