We're coming back to the "digital is digital" argument, which I'm afraid isn't true. Your amplifier and speakers can only reproduce and amplify the signal they are given. The positive thing about a digital signal is that it is clean, but that doesn't mean you can use any digital signal successfully in every system. Many digital products seem to work very well within a quality band of accompanying components, but once they're out of their comfort zone, seem to start adding harshness and/or start to sound a little flat.
There are demonstrable differences between CD players, and I myself have taken part in a blind test with three different players back in the 90s. As I said, my purchase of the Zenith was based on its comparison to the Zen Mini, both being fed into the same DAC in the same system (Classé and KEF Blade 2) via USB. At the time I was just going to replace my MkI Zen Mini with a MkII, but after hearing how good the Zenith was in such a revealing system, the decision was made for me. Whether it is the triple linear power supply or the SSD storage (or even a combination of both) I don't know, but the difference was easily revealed in that system.
Even CD players employing the same DAC can sound different due to their handling of the analogue signal after it has been converted from digital. Of course, a suitable system is needed to appreciate these differences.
Most analogies aren't 100% accurate as you're usually comparing chalk and cheese, but they usually serve a point well. I'm sure you get the point I was making.