Best digital format (non streaming)

You are completely right (and wrong) by saying 'cart before the horse'. 40 years ago when I got into 'music', we already found ourselves 'putting the cart before the horse'. We (handful of friends) found ourselves with a decent stack of CLASSIC music (16-20 year olds !!!). Why? Because back then, rock/pop recordings were JUNK, and we soon found that using those to evaluate our systems was USELESS. And yes, back then and to large extend now again, I (engineer) like hardware part game (constantly evolving, comparing, improving) at LEAST as intriguing as the RESULT (listening to a song or a piece). 

I find this behavior not really that unusual; it is almost the standard for example in my other (performance cars) hobby, where everyone is constantly tinkering with the car to improve the performance, yet no one really spends a lot of time to HARVEST the improved performance (for example spending hours per week on the racetrack). 

But yes, there is NO question that I (and those like me) have the cart before the horse !!! 

With that said: can you recommend some really (technically) good 5.1 SACD classical recordings?

That is what I suspect. The difference was too obvious to be explained with a bad DAC in the CD player (vs. the Modi 3). I need to read the (exhaustive) manual of the receiver and its setting to ensure comparability. 

I thought 'bandwith issue' was referring having to transfer all that 'stuff' through the 'airwaves' for 'streaming', and that is referred to BANDWIDTH (capacity to transfer data). 

It should not (hopefully) not be confused with reslution (24/192 etc). 

So rephrasing the question: best audio format/quality NOT streamed. 

Those pointing ad CD: is there really no better (higher resolution) media/files (commonly) available for purchase (for example through download and stored)?

Glad to hear that CD resolution still 'cuts it', since I am NOT and likely won't be for a long time a 'streamer'. And also came to find out that some 'remixes' (likely with much better resolution) and therefore 'better' are just not the same as the one made available to the public (for example on the original CD). 

And still the question (IF the 'raw material' is 'worthy' of high res processing/recording): where and how do I GET the high res file? I assume the streaming outlets only let you listen, but not SAVE the file. Likely, there are some (crazy expansive) specialty outlets that let you buy and download high res files? 

And only storage media will be computer/harddrive/USB/DVD-R/SSD? 

Or can I buy Dark Side of the Moon or Brothersin Arms in high res on physical media?

For now, I will tray give multichannel a first try, using a Sony X700 via HDMI to my Onkyo. I do NOT know what the signal format will be with this combination, but found it the only way (bought 2 SACD 'capable' players initially only to learn that they don't play true multichannel SACD only read the CD side) using HDMI with a Sony player. Not sure if receiver supports DSD, or if it will be LPCM or PCM. Receiver is Onkyo TX-RX810: 

Processing Features

• HDMI support for 4K/60 Hz, 3D, ARC, Deep Color, x.v.Color, Lip Sync, Dolby Atmos, Dolby TrueHD, DTS:X (with future firmware update), DTS-HD Master Audio, DVD-Audio, SACD, multichannel PCM, and CEC
• HDCP 2.2 supported on HDMI inputs 1-3, main out, and sub out
• Dolby TrueHD and DTS-HD Master Audio decoding
• AK4458 384 kHz/32-bit DAC (8 channels x 1)
• 32-bit digital signal processing engines
• Four DSP gaming modes: Rock, Sports, Action, and RPG
• Theater-dimensional virtual surround function
• Direct Mode and PureAudio Mode

• Atmos, TrueHD, Dolby Digital Plus DAC: AK4458 384 kHz/32-bit

  DTS-HD Master Audio DTS:X via future firmware update

I noted down the referenced sites for hi res downloads. I will visit and check out what they have (and cost). Thanks for posting.

"CD is best": I have a decent (for my level/aspirations) receiver with a DAC. And my CD player has also a built in DAC.

As a first 'try', I would like to compare the CD player analog into receiver vs. CD player digital out (and conversion in the receiver), using (depending on which CD player I uses) digital coax, optical or HDMI (?) to feed into the receiver. 

Is that a practical test? 

I was utterly surprised when I listened to my ripped CD played from my laptop via 25 ft USB C cable via Schiit Modi 3 analog into the receiver, vs CD player into receiver (computer sounde a LOT better). 

The difference was so obvious, that I actaully start to suspecdt that the RECEIVER is treating the analog in different (maybe has some 'sound enhancing' switched on) compared to the digital in from the CD player. I will repeat the test in 2 different ways: 

a) use the CD player ANALOG in the receiver and compare to digital input

b) use CD player ANALOG and compare with Modi 3 analog (again, identical CD and ripped CD). 

Darn! The better my system gets, the more I find it difficult to listen to 'old favorites' that are just recorded horribly. And lesser and lesser recordings 'make it' into the 'play list'. Now starting to look into classical music hoping to find some 'worthy' material. And relegate the 'old favorites' to play over a bluetooth box and computer speakers :-)