The issue of excessive gain is not valid. ARC preamps of 18 and even 30 db, e.g., LS5, is not an issue with many many amps. I have been using preamps of this gain range for 30+ years and I have been happy to have it….for phono and CD. Volume level and brightness are two very very different issues.
To claim that the CAT preamp is the cause of excessive brightness is also silly. This is a VERY dynamic and tonally neutral product that shows quickly the flaws elsewhere. And yes, it is very detailed. I had one on loan awhile back and it was incredible with my JL-3 amps. I just preferred the Aesthetix Io/Callisto preamp at the time because of the more warm and 3D of those magical pieces.
The Totem speaker line is also very detailed and dynamic…..incredible speakers. And they too will show system flaws quickly.
An evaluation of the cables (ICs specifically) should be done as this could be the cause of the brightness. What are you using here?
And what is your source? You need to evaluate the entire system and not blame the CAT or all the amps you are trying. It sounds like an overly warm amp like an older CJ or VTL or something like the ARC D70/D115 could be used to compensate for the brightness. But rather than finding an amp to compensate, you need to find the cause of the brightness and I assure you, it is not the CAT. And get rid of the Sovteks in the CAT if that is what you have there! Telefunken 6922's will add smoothness big time.