I have almost zero experience with the ST series. But, I do have years (25+) of experience with various DIY tube stuff. I am not talking about modded Dynaco ST-70's, here. I am talking about big and heavy, no compromise designs. (Although, I have warmed over a few Dyna's - they are really fun!)
Recently I plugged in a new 2B SST squared where my four chassis tube amp goes in my triamped system and after a few days of break-in, they are making some very nice noises.
I am so impressed, I have ordered a 4B SST squared. Highly recommended, IMHO.