I have not listened carefully to many high end streamers, so I am hesitant to weigh in directly on @kckrs’ question. But I have generally learned to trust the ears and collective opinion of people on Audiogon who have spent countless hours and dollars chasing audio truth, whether in the analog or digital realm. My first question when reading about the pluses and minuses of specific gear is “has the author actually listened to it and compared it to products B and C”? I trust vendors and designers generally when weighing in on design principles, but pretty much never on specific products, can’t help being skeptical of bias.
The old chestnut trotted out here that a streamer is “just transferring zeros and ones” and comparing word documents and spreadsheet data to digital music reproduction seems like a long ago dispelled issue and something that should only be reprocessed by zealots on ASR. Basing buying decisions or comparative arguments of potential sound quality in your room of digital piece A versus digital piece B only on specifications or bench top measurements seems only slightly better.
Reporting what experience I do have with inexpensive streamers, replacing the internal switching power supply on a Bluesound Node N130 with a Teddy Pardo external supply resulted in a major and easily noticeable improvement in the sound quality when used as a streamer/server and bypassing the internal DAC - more improvement than replacing the external switching on a Chord Qutest DAC with the same external power supply. Similarly, replacing the stock power cube on a Bluesound Node Nano with a modest iFi iPowerX in a different system significantly improved the sound quality of the Nano used as a streamer/server/DAC. So streamer power supply matters, a lot. Do I suggest here that these improved budget products rival bespoke alternatives? NO, I do not. Does this experience help me see how more sophisticated power management in a high end streamer could pay big dividends? YES, yes it does.
Extrapolating, in addition to the power supply in the streamer directly affecting the sound of the device itself, any noise that the supply or other internal component generates and is either injected into the mains or possibly affects devices or cables nearby can in theory negatively affect the sound of your hifi system as a whole - I.E. what you hear out of your speakers in your room. So any design solution from quieter power supplies to internal shielding to heavy aluminum casework to galvanic isolation can, in theory, improve overall sound you experience.
kn