Hugh, did you get the motherboard mentioned at the beginning of the thread? I'm interested in the Dolby Home Theater capabilities.
On my current HTPC, I just discovered that similar capabilities driven by DTS Connect only work when routing audio through the Realtek S/PDIF output. When I switched it to HDMI, the audio all went through the AMD HDMI Audio driver which brought everything back to the standard 2-channel PCM audio or pass-through AC3/DTS.
So the question is... on that new Sandy Bridge board are the Dolby Home Theater capabilities available when audio is connected via HDMI?