I recently made a number of changes from stock. I think the biggest for your case was replacing the reverb send tube with a 12au7. Lower gain than 12at7 so your 2 is my 4.5, but its warmer , and able to go all the way up to 10.
Preamp tubes power tubes and bias are also going to have a big effect.
Clipping channel 2's bright cap or making it switchable is another thing to consider.