The first valve I changed on my SLP-05 was the rectifier. I started with stock tubes and finished with Blackburn. Day 1 and 2. I left the rest. They were matched very well.
Did it make a difference? I was going to sell the unit if I couldn’t contour the tone. It added greater detail in every region. I ordered a STR-1002-SUPER rectifier from STL. I also ordered their passive tube 15 band EQ with a STR-1001 for it. BOTH are "Super" rectifiers. I use a STR-1001 on a Decware ZP3, literally night and day.
Does it make a difference? This discussion reminds me of cables and fuses. There is the "show me", bunch and there is the "I tried it" bunch.. I’m in the latter. Everything matters, even driving home with the window down before a listening session.