It looks like AMD's fusion makes the perfect HTPC. It will play any 1080p media file at about a 25% load. The max draw on the system was 51 watts, including SSD and 16GB of ram and PSU inefficiency. I would guess a 100 W PSU would be perfect for this system. Anyone know of a cheap, fanless silent ~100 Watt PSU? I'm familiar with the Kingwin STR-500 for $160, but that is massive overkill for this system. Doesn't need SLI or even more than one SATA connector.
I'm running an AMD fusion board paired with an Antec ISk. Check the link in my sig for build details. I've changed a few things since then (different SSD and different tuner) which lowered my power consumption, but it's basically the same.