I have run a lot of Sophia tubes including different 300B, 6SN7, 12AU7 and a couple others. I do like the 6SN7 and it was standard in our Purity Statement preamp. I love their 300B tubes but now looking at different options for the new Purity 300B buffer. Did not find the 9 pin signal tubes to be anything special.
Do this day, I still run their 274B tubes including the rigid.