Okay, the HTPC will stay on 12 hours per day, but what will it be doing during those 12 hours?
Both AMD and Intel CPU consume very little power when idling, but if they are active then AMD CPUs will consume more power than Intel CPUs. Therefore, I assume you want to avoid AMD CPUs in that case. For example, the power difference between a core i5-4670k and FX-8350 when encoding video at stock speed is a little more than 100w with the FX... umm.... winning this contest because it consumes more power... (higher is better...)
Do you have a budget?