Do Streamer only devices really impact sound quality?

Individuals use usb because it has best SQ vs other inputs/outputs available to them. I've observed many trying coax, AES/EBU, I2S inputs on dac, finding them inferior and returning to usb

@sns IME no…just, no.  That may be your individual experience and can always be gear dependent, but other than Holo DACs I don’t know of any other DAC manufacturer that recommends USB over i2S or AES/EBU.  For example, I fed my Musician Pegasus DAC via a high-quality USB cable and then bought a Denafrips Iris that let me use the Pegasus’ i2S input and it was a whole new world of performance and I ain’t no way going back to USB.  What USB versus i2S or AES/EBU connections have you tried personally and with what equipment?  You can cite “other people’s” experience all you want, but unless you’ve done it yourself, as I have, you’re just propagating hearsay and nothing more.  Back up your, frankly, controversial contentions with actual experience or this is just audio flimflam based on nothing and counter to what most have experienced here. 

Didn't Alvin Lee state that when using the Node with any of the Denafrips streamers that USB was the preferred connection? I think I read that here on AG, but can't find the specific post or remember the reasoning for his comment .  

@soix Do a survey, how many using usb vs other inputs. I had Singxer SU6 in order to try I2S with my present dac, a couple other individuals with same dac tried I2S, returned to usb after less than satisfactory results, I didn't even bother, sold the Singxer. USB inputs are optimized in many dacs, preferred by many. Do you have proof that other inputs superior to usb on all dacs? I didn't think so.

Individuals use usb because it has best SQ vs other inputs/outputs available to them. I've observed many trying coax, AES/EBU, I2S inputs on dac, finding them inferior and returning to usb.

I don't know that the channel itself necessarily makes that much difference, to my ears. What makes a SQ difference, to me, is the various DSP options I can get (or cannot get) via one channel or another.  I need a USB connection to a Macintosh computer in order to run BAACH4Mac (a spatial audio processor). I need a USB connection to a Mac, or to a dedicated music server (with an ultraRendu in the middle), to run HQPlayer (which offers many filtering and upsampling options).  If I want multi-room playback, I cannot run either of those processes, so in that case I use ethernet (or, in the past, coax or RCA analog).  If I want to play TV sound through my HiFi, I need Toslink (because my system does not have a complete HDMI ARC path from HiFi to TV and back).

IOW, functional requirements  (as well as SQ) dictate the choice of streaming signal path, for me.  I've had at least 4 different streaming pathways in my system. These include the Bluesound Node 2i (which FWIW has one of the worst ASR measurements for a device of its kind) and also a Matrix Element X (which FWIW has one of the best ASR measurements for a device of its kind).  I haven't noticed enough SQ difference among those paths, per se, to override the functional differences.  And without going to a ~$30K T+A streamer/DAC (one  that supports  the NAA protocol), I doubt any of them delivers enough SQ improvement to justify doing without HQ Player (or BAACH4Mac).  Which I'd like to do, just to simplify the chain. But I'm skeptical that a change of streamers alone can make my soundstage sound about 50% wider, as BACCH4Mac can for some content.