Switching to solid state amp?

Russians have been making great tubes for ages. They still do. There are also excellent Chinese tubes.
As for the future of tube equipment, I don't know. It might be doomed, it might be not. There are enough good tubes for our lifetime, though, just will be getting more expensive, perhaps.

@inna   Thanks for the added info and clarification. That's good to know, despite the price differential.

Anyone who has heard both?

In addition, Diablo 300 DAC option is much more expensive, and you can have both phono stage and DAC in it, Diablo 120 is either/or only.

One could make a case to move from tubes to SS because they prefer the sound of a SS amp as that is a decision based on personal preference. One can also make a case that they don't want to pay for tube replacements. That is also valid with amps with expensive tubes (ie. 845's or 300b's) but if one is careful in choosing a tube amp they can buy one that doesn't use expensive tubes.

But to say one wants to go back to SS because they are easier to maintain or are more reliable is not valid. A point-to-point wired tube amp, with no printed circuit boards is one of the most straight forward designs to diagnose and repair.

I will look at the Octave it could be a good choice.  From what I have learned about the Diablo 120 the build and parts are quite equal to the Diablo 300 but the 300 is a brute.   I am sure the transformer is beefier but both have the same house sound.