At first: Thanks for the answer.
Second: I am a german and my English skills are poor - I use "Google translate", so please excuse some oddities - at least, those who are not in my personality, but in the translated.
Well, there you are in principle right, but not in detail - I did not think of the possibility that iTunes down sampled.
I also think nothing of hi-fi voodoo, cable sound is nonsense, (with neatly clean wiring (connection values!) It makes no difference whether I use 10/20Euro cable or 1000Euro cable.
Similarly, the difference between amplifiers is negligible, 1. as long as the amplifier is not sounded and 2. the amplifier has the loudspeaker under control - with my previous Elektostat Acoustat 2200 (overhauled) with 1.5ohm minimum, violent phase rotations and efficiency of about 80db it's no wonder that most amplifiers could not cope with that.
(Incidentally, the power amplifiers from the Harman Kardon Festival 500 system did it without any problem - more than little high volume on the electrostatics - if you are looking for a very good, absolutely stable, cheap, excellent little power amp: Harman Kardon Festival 500 (2x 60Watt) with the festival Preamplifier - if you want to use the power amp solo or on another preamplifier, you need to rewire a small bridge in the power amp (> Internet) - You almost get knocked over by the Festival 500 systems.)
BUT: Even if I only listen to 12khz (60 years old), I have the experience that I hear resample, partly much worse (with JRiver 48 / 96khz upsample> 384khz = horrible - much worse (Cable DAC, Aune S1 and the same with other Douc audio)
Other resample rates - down or up - I hear synonymous (some minor differences)
When I listened to CD in the 90s, everyone was enthusiastic about CD ...... I did not, or only with restrictions.
Solo instruments, voices, sparse instrumentation was partly fantastic with CD, partly better than with LP.
But as soon as it became more complex - big orchestra, many instruments and even more, if it was still loud - broke the sound literally together: my system sounded 2-3 "classes" worse.
All in all, listening to LP was better for me because it was more balanced.
From 2003 to 2016 I could not hear or compare hifi anymore. Have again a turntable Thorens TD160, My LPs have to be washed but first .......
Long story, short sense: I would like to send with JRiver 96khz or more via Wlan/DLNA.
BUT it can also be, that the Kef X300a wireless is only able 96khz on cable, and not on wifi/Wlan - I have found no information in the WEB. I will ask Kef.