We were discussing the benefit of the Pro Plus versus the Pro. I had assumed, wrongly, that the AS501 would have a better measuring DAC implementation than the Pro and therefore suggested using the Pro simply as a 'transport'.The benefit of the PRO model is its better DAC. Therefore, if the PRO is being suggested, using the line out to the Yamaha makes more sense.
Also, I was asking whether the OP uses a subwoofer as I was assuming the AS501 would need to digitise it's analogue inputs if you're using the subwoofer output/bass management and that would negate any benefit to using the Pro Plus for it's superior DAC.