A lot can be learned from these demos: 1. Does it sound like music? 2. Is music distortion free? 3. Is there a lot of detail? You can't fake any of these parameters. You can also get a better "feel" with headphones (if used). These demos are a lot better than nothing.
Most impressive youtube demo clips
What are some of the most impressive clips of systems you've heard? This one blew me away with how tonally rich and real the guitar sounds. Sounds like you're in the room with a nice tube guitar amp.
Spatial M3 Turbo S + SPEC RSA-717EX + Denafrips Terminator DAC
https://www.youtube.com/watch?v=rrvx2bx2Cgw
Spatial M3 Turbo S + SPEC RSA-717EX + Denafrips Terminator DAC
https://www.youtube.com/watch?v=rrvx2bx2Cgw