BB, I've done extensive critical listening to the NOS 6H30DR tubes, and they do impact the sound in a significant manner in my system. As additional pairs are added to the power module, there is increased dynamics, resolution, and frequency extension. I would almost describe a more 'powerful' sound.
However, in my system, there is a downside. With all 4 pair, the music is less cohesive and parts of the frequency spectrum begin to stand-out. When this happens, I think, "This is a recording", and the illusion is gone. Removing the tubes and going back to Sovtek, I notice a smoother and more even sound.
I have found a happy middle ground with 1-2 pair of NOS in the power module. I have some increased dynamics and treble extension, but do not lose sight of the big picture. I have had negative results with the 6H30DR in the switched position within the main unit - I clearly prefer the Sovtek new tubes there. Likewise, I prefered the Sovtek 6C45 compared to a NOS version.
I think your appreciation and the number of pair will depend on your system and musical tastes. If you like jazz, pop, and rock, then it would not surprise me if you preferred all 4 pair to be NOS. For classical music, 1-2 pair may be enough. So, I think you should buy 2 pair to try as a start, and take it from there.
In addition, I could recommend the EAT Tube Dampers x16 (they won't fit on the GZ34/5AR4s. They create a more solid and full sound, and do not make the sound dull or overly damped at all. Also, do replace the fuses with Hifi or Furutech, and apply Quicksilver Gold to the fuses and cold connections (extremely sparingly).
However, in my system, there is a downside. With all 4 pair, the music is less cohesive and parts of the frequency spectrum begin to stand-out. When this happens, I think, "This is a recording", and the illusion is gone. Removing the tubes and going back to Sovtek, I notice a smoother and more even sound.
I have found a happy middle ground with 1-2 pair of NOS in the power module. I have some increased dynamics and treble extension, but do not lose sight of the big picture. I have had negative results with the 6H30DR in the switched position within the main unit - I clearly prefer the Sovtek new tubes there. Likewise, I prefered the Sovtek 6C45 compared to a NOS version.
I think your appreciation and the number of pair will depend on your system and musical tastes. If you like jazz, pop, and rock, then it would not surprise me if you preferred all 4 pair to be NOS. For classical music, 1-2 pair may be enough. So, I think you should buy 2 pair to try as a start, and take it from there.
In addition, I could recommend the EAT Tube Dampers x16 (they won't fit on the GZ34/5AR4s. They create a more solid and full sound, and do not make the sound dull or overly damped at all. Also, do replace the fuses with Hifi or Furutech, and apply Quicksilver Gold to the fuses and cold connections (extremely sparingly).