I don't see two different DACs being used for the same analog output. The two channel output has its own differential dac. And the 7.1 channel output has its own set of non-differential DACs. I don't think the audio priority has anything to do with what DACs are used. It is more for handling the dsp load. For example, if multi channel is used then the dsp is focussed on getting7.1 audio out and does not process Audio for sending through hdmi. If hdmi is used, the multichannel 7.1 outputs 2 channel only. I don't think any of this affects the 2 channel output. Just my educated guess.