Not limited to Aurender, a high quality clock is usually one using OCXO or Femto and “quality” is about accuracy of timing, just like a luxury watch that uses a mechanical design to keep time. The clock’s role is focused on the transmission of digital samples and how well it assembles those samples back together. I wrote in a different thread, but clock and digital playback accuracy can be compared to photography. Many cameras and lenses can take a photo, and many of them do it “well”. But some stand out because of the quality of the lens in reproducing exactly what is out there, and the image is crisper, more natural, and the colors do not bleed due to aberration. A great clock does the same and results in the most accurate timing of digital signals, which will result in clarity, separation, and coherence. A lesser clock can still reproduce well, but in comparison to a great clock, it’s as if the image just wasn’t properly focused ever so slightly, or a slightly inferior lens was used. Sometimes one cannot tell unless comparing the two photos side by side.
Higher end Aurender’s do leverage better clocks, but they also leverage more robust power supplies, better isolation (both in circuit design and chassis), and other benefits.