A true SET is A single ended Circuit within. That one Tube per channel capabilities,when you use say 2 -300b tubes Around 20 wpc or any set type tube
your circuit starts getting more complex and start going into class A mode which takes away from the absolute purity of the SET design Still very good , That is why you will never see
a pure SET amp with more then around 8wpc . In design it goes deeper then that just look up a true SET Vacuum tube circuit .In its simplicity
a 300 b excels in the midrange thst is why many use these with
104 db klipsch a Khorns or Voxativ drivers for example .
or even a external powered sub .below 100 hz.