Signal tube versus power tube, sound impact?

I went back and forth experimenting with tubes in a little Japanese 300b integrated amp in this case the small 12v tubes definitely made a bigger sonic impact on the sound. There was a very big gain in the bass region

Seems to me the preamplifier tubes Carry the most weight when dealing with the sonic signature. It's at the beginning and why would you not want to amplify a quality signal right away. If you have a crappy preamplifier tube it's going to get amplified and sound crappy no matter how good the rest of the tubes are .

Anyone ever see a good diagram showing the circuitry flow within an amplifier or a good walk-through of the incoming power and incoming signal and how they ultimately do stuff before they go through the Cable leading to the speaker? And of course showing all the various tubes in series etc.  

Pleased to hear the opinion that power tubes matter more than signal tubes (only because that's what I have found to be true and I'm a confirmation whore.) Shirley you must know that this flies against common wisdom that pairs tube preamps with solid state power amps. 

Seems to me the preamplifier tubes Carry the most weight when dealing with the sonic signature.

This has been my experience, except in the case where the tubes in my amp were getting worn out & tired.

Shirley you must know that this flies against common wisdom that pairs tube preamps with solid state power amps. 

@mambacfa  , I cannot find the post in which Shirley weighed in on this one.