I have to do some digging into the AVM 70, because for some reason I
seem to remember Anthem would route even analog input signals to the ADC>>>DSP>>>DAC path whereas D,M and Y would bypass them in direct mode.
Purely based on specs and measurements the Gustard X16 is of course far superior as you are talking about at least 20 dB difference in THD+N based on bench test results. I doubt even real certified golden ears can hear the difference between -90 dB and -120 dB THD all else being equal, under normal conditions even in an extremely quiet room with 15 dB noise floor.
Just for fun though, now that I have very quiet Hypex and Purifi amp, I was able to use one of the amps to compare the hiss/hum between my AVR-X4400H and AV8801. Amazingly, the AVR-X4400H that has at least two octopus sucking on it, including fibre TV, Fire stick, Apple TV, 3 power amps, 3 Ethernet hubs, PS4, 3 BDP, 1 HDDVDP, 2 Active subs and 11 speakers, was audibly quieter than the AV8801 that only has the aux XLR input connected. So much for those copper shielding, copper mounting plate and balanced I/Os.
![Frown :( :(](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
With the Denon, I could turn the volume to maximum, that is +18 and could only hear something with my ear touching the speakers, and I am very sensitive to hum and hiss.