I have been back to running NOS. Sylvania Bad Boys in the output stage
I lucked into a pair of those ('52s I think) and have been running them in the balanced input sockets iof my SLP05. I love them. "The Iron Fist" is what the individual who gave them to me called them. He also gave me a pair of National Union 6F8G that he described as "The Velvet Glove" and I like them, but for different reasons than I like the "Iron Fists." If you wanted to try 6F8Gs, you would need adapters.