Amplifier Power tubes - important to sound?

I built an EL84 Single Ended amp. The donor amp camp with some JJ’s. Amp was very much missing something with the JJ’s. Ordered a pair of The Tube Store preferred series 7189’s. 
 

The amp changed completely in its sonic presentation. It now sounds how I hoped it would sound. 
 

But, as a single ended amp, swapping out a tube in this simple a circuit, will showcase tube differences kind of dramatically 

@emergingsoul

It’s so strange. I want to believe that your just putting us on, but in the end, I actually think that you’re really serious.

that depend on the amp and the circuit. more feedback = less audible sonic difference in manufacture of tubes. 

@emergingsoul 

I sell tubes full-time for a living and I think you'll be looking for those elusive Siemens' 6550s for a very long time indeed because I don't believe they exist. 

I love Siemens tubes and I'll tell you the closest thing to what I imagine a Siemens KT88 or 6550 would be/sound like that you can buy is the modernly made KR Audio KT88. At $400 a pop they aren't cheap and they are about as hard to get your hands on as the fabled Siemens 6550s. They are a nuanced, disciplined tube that is subtle in how great it is such that trained ears might appreciate it far more than ears just looking for "more."

Many say the KR Audio KT88's sound like NOS GEC/Genalex tubes. But I doubt too many of the many that say or have other opinions or claimed knowledge about them have ever actually heard them never mind spent the time to listen to them. I swap my KRs for my GECs on a weekly if not daily basis, and have for years, so I'll tell you that in the I don't think they sound similar at all. In fact, I always tell people if Siemens ever did make one, I expect it would sound like this (the KRs). And now I've told you, do what will with that.

Rockets,

Yes power tubes have the most impact on sound. Next are signal tubes. Further, the first signal tube in the series has the most impact on sound.