Ah, yes, the good old “your system isn’t resolving enough and you don’t have muh golden ears” song and dance.
Despite having “psycho” in the name, psychoacoustics is an actual science. And it does not work the way you think it works.
When you listen to a setup for several days it only shows whether you like (perception) whatever you paid big money for. In a week you can convince yourself, unconsciously, that you like or do not like something based on an number of factors none of which have anything to do with the physical phenomenon of sound waves emanating from your speakers. Subjective stuff. If it makes you happy, enjoy your system, but it says absolutely nothing about there being any real difference between two components.
The only way to determine if there is an actual difference between two components is to perform rather extensive measurements. To determine if there is any audible difference is to do a proper (level-matched etc.) blind test. Which needs to be done within minutes. No one can remember subtle details of a sound even over tens of minutes, let alone days. If you reliably hear a difference in an ABX test, it exists. If you don’t, it does not. All that you have “proven” to yourself is that you want to believe that you did not waste your money.
Incidentally, speakers, room acoustics etc. have no bearing on anything that happens from your source component all the way to DAC’s output. Connected to the same source, same DAC in my room will output exactly the same signal as it does in yours.
Besides, saying that, assuming at least an asynchronous USB connection (so we don’t have to deal with source vs. DAC clocking and jitter in crap legacy interfaces like S/PDIF and I2S), using a different source to the same DAC would produce materially different output goes against all the science used to actually develop those DACs. It’s an extraodrinary claim requiring extraordinary evidence. Should we believe people who invented digital audio or people who want to either sell you something, or to convince themselves that they did not waste good money on buying something useless through a completely meaningless experiment that demonstrates nothing?
