I like the custom trans route; over designed for the projected application. The old guys favored certain tubes. Assuming we eliminate the financial reason and the ease of getting that tube then we must assume they had solid reasons for using the more common tubes. What are those reasons? KISS as always. Size; I like big amps. They always sound better. Not in total watt output but in physical size. Triode wired choke input. I like PP amps but I also have heard nice SE designs; so thats a wash. My 2c.(Must work well with G)