Discerning a difference between streamers is difficult...only me or common for all?

My experience with streamers have all been custom builds, learning from 'expert' members over at Audiophlestyle forum. Each has had unique sound qualities that were easily heard. Over time I discovered power supplies most greatly impacted sound quality, quality of parts populating motherboards, operating systems and music players also affect sound quality in my setups.

Optimized interfaces also critically important for both streamers and dacs, some of these streamers not optimizing usb and I2S interfaces to their fullest, this means highest quality clocking and power supplies for those clocks. Many are adding a second streamer to these off the shelf streamers. These second streamers act as endpoints only, therefore, they contain motherboards and operating systems designed for a single purpose, which is to act as that endpoint, point of this is to minimize self generated noise, provide lowest possible latency. The second purpose of these steamers is to provide a more optimal usb or I2S interface, this means better clocks and power supplies than provided by many off the shelf streamers.

Unless all these off the shelf streamers using very similar power supplies, parts I find it hard to believe they all sound that similar. But then perhaps they do, evidence of that in this thread. I look at something like the highest end Taiko servers,  based on reviews these are game changers. Streamers at this level take every concern I've listed above, and there are more, and concentrate a level of engineering such that self generated noise and immunity from external noise creates a nearly unlimited noise floor which means higher resolution. They also have proprietary and optimal interfaces which surpass commonly found usb and I2S interfaces.

I’ve gone through a half dozen streamers topping out at a $6500 Aurender. I found it makes very little difference depending on the DAC you are using.  For me once I got a very good DAC I found the differences between streamers to be almost negligible. At this point I now recommend to friends to find a streamer you like the software/App for. That to me is the deciding factor now, ease of use and sound cataloging.  

I did a test using red book digital quality (CD) through my Aurender and Apple TV box both directly from tidal both into the same DAC, surprisingly the Apple TV box was not significantly worse than the Aurender, actually very little difference. Granted at red book not hi rez formats. My optimized PC is actually slightly better/same as the Aurender, and I’ve since sold the Aurender. I won’t be wasting big $’s on streamers anymore.

OP - I, too, was prepared to climb the upgrade ladder on streamers but have creased, at least for the time being.  I went from a Bluesound Node 2i using its DAC, to using the Node 2i as a streamer but a Cambridge CXA81 DAC, to a miniDSP SHD streamer/DAC, then back to a Bluesound Node 130 with a LPS into a modded Peachtree Gan1 power DAC.  Now I have implemented the Bacch4Mac and Bacch ORC system; I simply use the Qobuz app on the Bacch's Mac mini fed into an RME interface and then to the Gan1.  All along the streamer is fed by Ethernet via an English 8 switch.  To be sure, I haven't compared SQ with any of these configurations to one with a high-end streamer like Aurender or Innuous.  For me, so far at least, the big gains in SQ were in the DAC, the Bacch processing system and the power amps, definitely not the streamers.  In fact, what I found was that the big difference in streamers came from their user interfaces, not SQ.   I really enjoy the music now and have no desire to upgrade anything.  Best of luck.

I'm not sure my experience will be all that helpful but here goes. I have three Auralic streamers in three different systems: an Aries Mini plus S-Booster LPS, an original Altair, and an Altair G2.1. These were purchased over the course of some seven years, with the G2.1 arriving a month ago. (Auralic was blowing them out at nearly 60% off, no tax or shipping, to make room for the G2.2, and I couldn't resist.) I only stream Tidal, not files. In  my main system I listen almost exclusively to vinyl (two turntables, four tonearms, three phono stages). Each step up the Auralic line has yielded obvious improvements in SQ. Stark, not subtle. Just to be sure, I compared them in my main system. So IME, at least with offerings from a single manufacturer, the differences are clear. Whether differences would be audible between manufacturers at the same level of component I do not know. I will say the G2.1 sounds remarkably good, even next to my high-end vinyl rigs.

I used to be a big doubter that there could possibly be any difference that you are actually hearing rather than just perceiving due to expectations, subconscious or otherwise. I now am convinced due to first hand experience that things can get weird and go wrong in all sorts of unexpected ways. Technically nothing should be perceptually changing, but that assumes everything is working correctly. Some faults are so obvious nobody would deny it if they heard them. For instance, if I use Apple Music to stream from their service, every song has a short stutter near the start of the song. This is a well known issue that Apple doesn’t seem to be able to fix, and it isn’t the same for everybody. Somewhere there’s a complex wrench in the works. Something ain’t right, and it makes you wonder what else ain’t right that might be more subtle and intermittent, thus not always showing up on single measurement tests. If I rip my own discs and don’t stream, it never stutters. Other streaming services never stutter.

I’ve got a device that runs optical audio in to my computer via a USB converter. It is unstable, and sometimes it does really weird things. If it gets bad enough, the music just stops.

On my Blu-Ray player I sometimes get audible and visible static. Just touching the HDMI cable will usually stop it for a while. Bits is bits, but they don’t always show up at the right time.

So, maybe you’re not hearing much because there wasn’t much going wrong in your particular system in the first place. I’m assuming here that in many lower end systems, like mine, many subtle things might be going wrong that happen to much less of a degree on better systems like yours, especially if you happen to have good synergy between your components, even if they aren’t at the very highest class levels available.