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

Streamers are simply specialized computers. They rely on hardware and programming. So differences in streamer sound can exist but the differences when present are often hard to detect without direct a/b tests.

For example, I did a/b comparison of sound between Plexamp and “vanilla” Roon streaming software prior to switching to Roon and the difference in a/b testing was clear and profound.

But even Roon’s sound can vary to a very great extent when DSP functionality in Roon is applied.

Digital streaming is a whole new world when it comes to sound quality. Pretty much anything is possible. The good news it’s not that hard to do well and most even decent quality streamers do a good job making good sound more widely available to more than ever before. But streaming is like beautiful women. There are all kinds and no two are often exactly alike.

One thing to consider is that audio memory is fleeting.  Unless you are able to switch quickly from one set up to another and have them be volume matched to within 0.1dB, making a comparison with any veritas is difficult at best unless maybe you are playing a specific snippet of music that has something in it that you are noticing for comparison, say the sound of a kick drum or a flute or whatever. 

Some reviewers, for what it is worth, which might not be much, do say the new Node Nano is extremely good for its price, besting the Node X, and if you are using it to feed an external DAC, it simply might be doing a pretty darn good job of it. 

Ultimately, I think you may have reached a point of diminishing returns. Time to just enjoy the music and be happy, especially with that AR DAC 9.  Your room and of course your speakers are probably making far more difference than the difference between streamers fed into an external DAC, especially if the external DAC is doing its own reclocking. 

Thanks everyone for the reassurance as I feel this digital world is a bit unique in how we can build a great system

I know @ghdprentice has had a different experience as I have read his posts of how his system improved with each advancement of streamer

someone mentioned pianos and how they can pose challenges for systems in their reproduction of the natural sound.  I mainly listen to classic rock, jazz, r&b and blues so maybe my music taste is also not as demanding.

there is also no one size fits all or even one shoe works for all

on a side note, my favorite 2nd cousin(same age)brought her husband and 3 kids to my home for thanksgiving and her oldest daughter(20)was blown away at my 1500 records and I am excited to put together a bundle of records for her as a Christmas gift...my heart will always be in the groove

You're not crazy. I have a $2400 streamer and a $500 fed into the same DAC so I can instantly AB and I'm struggling to hear a difference. Or I believe I hear one, only to go back and explore again and poof! The difference is gone or subtle at best.

But I keep trying. I realize we trade in nuance and subtlety in this hobby. If I got a subtle but definite improvement, I would pay good money for it. My system is highly resolving so every bit matters (to me).