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

I'm using an ASUS gaming computer running Windows 7 and Qobuz for streaming. It's going into a Berkeley Alpha USB which is connected to a Berkeley Reference MK II DAC. I also have a Jay's Audio CD3 Mk III transport hooked up to the same DAC.

I have compared streamed files from Qobuz to the corresponding CD at least a dozen times (being careful they are the same version) and I can't hear a difference. If the computer is adding noise or some other kind of distortion to the music I can't hear it. I am skeptical that a streamed file would sound better than the corresponding CD played though a state of the art transport into the same DAC. If they sound the same I think that's about as good as it's going to get.

If someone has a streamer and a CD transport I suggest using the CD as a control. When you just disconnect one streamer and hook up another one it's very difficult to accurately compare them. When you use a control, such as a CD, you can remove some of the possible expectation bias that we all have.

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.