Solaris and RKV3 are basically identical amplifiers, but twice as powerful as luminaries. We switched to a different tube type 3 years ago from PCL805 to ECL65 / 6F5P.
The PCL 805 tube was no longer available worldwide and ECL85 has been able to secure many thousands of pieces for us.
So today, the performance data are slightly higher in comparison to the models before 2015.
Luminare has 2 x ECl85 per channel and delivers about 8 watts per channel. The two larger products bring have 12 watts per channel.
Since the chassis of Solaris and RKV 3 are almost identical except for the STAX function, it can be assumed that both sound the same.
Overall, the larger amplifiers are sovereign, because they have more reserves.
We still have some sources of information about Luminare, Solaris and RKV 3 available for you to visit.
They are partly German, partly written in English and give impressions from other users.
:
https://audiovalveforum.de/upload/forum/
and a big german forum
https://www.open-end-music.de/vb3/forumdisplay.php?f=225