I ran a test for grins last night - sighted as I was by myself. My Raspberry pi running Volumio normally connects to a Schiit Modius which outputs via balanced to my Luxman integrated. I ran a second usb cable from the pi to my IFI idsd Signature which outputted via unbalanced to the Luxman. Volumio lets me switch DACs then I just restart the song, switch inputs, match levels - seems to be 7 volume button presses higher for unbalanced. AKM 4493 in the Schiit and a Burr-Brown in the IFI. Once volume matched - no discernible difference. So, in this age of better and better measuring DACS - when does it actually matter. Once you reach that level maybe the real differentiator is features and reliability.