Hybrid SS FW bridge/tube FW rectifier for slower start up and better reverse voltage blocking than a pure SS bridge. DC on the filaments. Lundahl iron is big coin. For stereo: 2 interstages, 2 outputs and 4 chokes (the chokes are
not specified as Lundahl however) are needed.
In audiodesign's SE, he uses the same Lundahl interstage, but he goes volt amp -> volt amp -> interstage with a 6sn7, instead of the parallelish 6sl7 -> interstage as in diyparadiso.
You could go cheaper and just parallel a KT88 in the schematic (or a similar one) below:
If your intent with the PSE is go into A2, a chip amp -> Electra-Print interstage for the driver would be more reliable and cheaper than the 6sl7 -> Lundahl interstage. I do
not know how may clean Watts the 6sl7 -> interstage combo can put out, but a chip amp -> interstage can do around 10W, perfect for reliable A2.