Converting Classic Hi Gain to Lo Gain

I recently purchased an ST-120 and I'm just starting the build.
I'm a newbie to this... big time

I was just reading a bit on the Lo VS Hi gain. My ST-120 is the Classic Hi gain I believe as it is to run the 12AT7 tube.

I could see next Spring buying some nicer speakers 93+dB. I think the 93+dB it is better to go with Lo Gain over Classic Hi?

I may even go with the PA3 (PAS3) build kit or the VTA PAS3-Z modification. I'd like a Pre-Amp and could see doing that as a late winter/early spring build. Given that the pre-Amp is tube based I thought I should convert the ST-120 to the Lo Gain if I go with the tube based pre-Amp?

If you get the PAS3 kit with finished custom chassis for $499... What is the benefit of the VTA PAS3-Z 50$ upgrade? Sorry, newbie and I'm not registering it.

So back to the main question.. What do you have to update on the PCB? I know you run 12AU7(Lo Gain) VS 12AT7(Hi Gain). I thought some resistors would be De-soldered and swapped. Can you not update the PCB and just roll tubes and put some 12AU7s in and get Lower Gain?


PS - I did buy the 4 military-spec Russian PIO output coupling capacitors

And sorry for having a post with 9 questions.

I was told by a guy on audiokarma the other day that the use of negative feedback alows the amp to compensate for lower mu tubes in a circuit that uses 12AT7 or AX7, so I'm curious about this as wel.