Hey Plus 1,
I can provide information on the saturn, Isis and Cambridge 640c. My 3 silver spinners prior are too long ago for comparison.
I upgraded from the Cambridge to the Rega SaturnR.
The unit absolutely tired me out with the scope of musical information presented. Absolutely blew me away. I had purchased some sonus faber Cremona Me and wanted better digital source.
The Azure 640c was mushy instrumentaly and could not compete with the Saturns R's detail retrieval, tonal scope or timbre. The SaturnR though did not provide the 3d stage depth I was chasing, stringing the stage out like a pair of phones.
Musically I could not fault it. Get the unit side by side with good vinyl you will know what I mean.
Ok I wanted more, absolute longevity and 3D presentation. Got the finances orderly and purchased a demo Isis. The outcome is way more than I could have expected, I enjoy music way beyond my usual taste and the sum of the parts absolutely squashes the idea of diminishing returns.
WhatHifi did a review a long time ago, much of which was valid, particularly pairing with the Osiris amp to overcome the bass heavy Isis, which I eventually did.
But the nuanced tonal depth across the spectrum and instrumental timbre/signature identity is beguiling. The disc information retrieval will push past vinyl but the sound signature is different. You won't debate the two sources, the quality is way beyond those arguments. Hope this helps.
You won't blow your money but you may not purchase another spinner beyond