This project was trigged after, actually having seen an idea for such an amp, but more after eyeing up a design with four E88CC/6922.
I choose 6SN7 as I had several Russian 6N8P (equivalent to 6SN7) and I wanted the higher power from the 6SN7. Someone checked the original and came up with a modified schematic, solving some problems in the original.
The original 6SN/PSE
The modified 6SN/PSE