But not to do the mistake thinking that the brand components will afect as same as a good circuit design.
Do you have very much experience modifying or fixing amps?
I can tell you from 1st hand experience that a "Good Amp Design" can only be made better by using top-of-the-line components.
Your arguement that Capacitors don't affect Tone is not valid to any extent. Every component in your amp will have some sort of effect on the overall Tone. I don't give a **** what any Egg-Head with an engineering Degree (although I have one too) says. Most tests are conducted using "Audio Amplifiers," which need to stay as Linear as possible, with as little Distortion or Noise as possible.
I also don't agree with the whole NOS thing. There is not a Vintage amplifier on the planet that sounds exactly like it did when it was new. Also, most of the recordings that we are used to hearing from this era have lots of studio magic, Tube Microphones, etc. mixed in with the Vintage Gear.
We are talking about Guitar Amplifiers here. Most of us try to get the most Distortion we can out of our amps.
You are also generalizing the entire scope of parts substitution or modification. Certain Mods can affect the Touch-Sensitivity of the amp, and leave the overall Tone unaffected. Other Mods can do the opposite, or any number of things. Just because you like the Tone of your amp doesn't mean that everbody else will.
If everybody was happy with their Fender amp, there would be no Mesa-Boogie.
If everybody was happy with their Marshall, guys like Lee Jackson & Mike Soldano would be bussing tables instead of making millions.
Here is a real-world example or 2:
'67 Fender Deluxe Reverb:
1. Lots of noise, and crackling in both Channels, due to older Carbon Comp resistors on the grids of the Pre-Amp Tubes (100k ohms).
I could just replace the Carbon Comp with the exact same part, or I could use a Metal Film resistor instead. This is entirely up to the Owner.
The Carbon Comp will not change the overall Tone of the Amp, but will change how much Gain the amp has if I use a hew 100k ohm resistor. The original part was not exactly 100k ohms, it could be off by + or - 5%. Now we add 30+ years of drifting farther out of spec and we almost always end up with 115 to 150k ohms on the actual part.
The Metal Film resistor will, however, change the overall Tone of the Amp, as well as the Gain if the value of the original part isn't matched with the new one. The Amp will sound much more focussed, with less overall Highs. The Amp will be much more quiet as well since even brand new Carbon Comp Resistors will create large amounts of Hiss.
The difference between Carbon Comp & Metal Film in a Vintage Amp can easily be compared to the differences between Records and CD's. Records are preferred by Audiophiles and so-called "Purists," due to the fact that the signal was recorded andreplayed entirely in Analog. I prefer CD's because there is less noise, they are smaller, and they skip less when I'm driving down the road.