To add I find that as the quality of my streamer has improved then the gap between CD rips and 24 bit downloads etc has closed. It does such a good/better job with 16/44.1 that Hi Res has less improvement.
To quantify I was always aware of the difference on my Linn Akurate DS more than than my Klimax DS.
Also consider Hi spec DAC's etc these days tend to upsample to say 384 Khz, process and filter in the DSP chip, then output to analogue. So your not comparing CD or MP3 level with Hi res, but upsampled vs native Hi res, which sure closes the gap, done well to something not detectable.
So if Hi Res is noticeable better, it's more a sign of how poor it's doing on standard 16 /44.1.......
All of this pales to nothing compared to the way the music was recorded, mixed and mastered.... Protools and direct to desk in my view kills music and it's flow and emotion.......