None of the APUs support dual CPU motherboards. Support for those configurations tend to be restricted to server chips like the Xeons from Intel and the Opterons from AMD. Consumer applications don't really benefit from a dual CPU setup, so consumer CPUs don't support dual CPU configurations.
In any case, most software would not benefit from a dual CPU setup, and no there is no way to set up the APU's graphics cores to Crossfire with each other on a dual CPU motherboard. That's why you can't find any benchmarks for that.