It is puzzling. I've seen instances and read about numerous tests where people hear things differently when presented with the same equipment and an A/B switch that's not connected to anything. Which makes things like human perception tests very difficult to perform properly to filter out biases. I remember one instance quite a while ago where one of the people who did the A/B test got incredibly irate, I mean just seething mad and loudly accused us of "tricking him" and was quite verbally obnoxious. Why that was the reaction is beyond me, when I first got "fooled" in a test that showed I couldn't hear what I thought I could I was really curious as to why, not pissed off about it.
I agree, the only reason to add a DAC is to add streaming capability. The idea of adding a CD transport and a DAC to feed an analog input on the Beosound then via analog PowerLInk or MasterLink to speakers is pointless. Now, something like a Core or such that lets you add streaming is a good way to modernize the system.
