Sick set up. Can you compare how the Riviera drives the Caldera vs your other tube amps?
Riviera is insane. No other way to put it. And buying is also insane. No other way to put it. I'm not going to attempt to rationalize it. but I will say the reward is just a tript oa nother domain. It's the most effortlessly delivered power I've experienced from any amp, and its hybrid design allows lots (really material) tuning of sound via a signale 12au7 gain tube, coupled with an outstanidng class A solid stage output stage.
The Riviera is excellent with the Caldera. For me, its main use is with the Susvara; that combo may be one of the most breathaking synergies I've experienced. It is also outstanding wtih thte Tungsten.
For Caldera, I personally prefer the Decware/ZMF combo above all else. But if one likes SS amps, the Riviera would be it.