Explanations from cheerful and serious people are quite enjoyable.

I’ve come to understand several characteristics of the RA Atalante 5 from analyses, but I now find myself grappling with a new confusion. The faint reverb following a finger snap, and a distortion that sounds as though the speaker playback is being recorded and then replayed—these were extremely pronounced when paired with the Electrocompaniet ECI 6DX MKII. A similar resonance, albeit less pronounced, was also evident with Yamaha’s R-N2000A. I attributed these sounds not to the signature of the speakers but to the amplifier's inability to properly control the speakers, resulting in a loose and weak sound. To avoid this, my options for amplifiers have become increasingly limited.
According to an analysis of speakers, I suspect that I tested the Copland CSA150 without benefiting from its bass buff. While there was no distortion in this case, and the Naim Uniti Nova PE delivered a balanced and firm sound without distortion, the high-frequency clarity was relatively lacking.
I find myself reluctantly praising Chord amplifiers, and the Ultima Integrated has become the standout in bridging this gap. At the same time, I am troubled by the thought that the sound I’ve come to regard as “good” may have effectively stripped away the true signature of the speakers.
Why does the serif-like reverb distortion disappear with certain amplifiers, leaving only a clean, sans-serif sound? And is this distortion truly inherent to the speakers themselves?