Seems like the best "upgrade" for tube amps....

It is possible that Frank feels that there is no substitute
for good engineering, even expensive parts. Case in point I
purchased a cheap chinese preamp, called Modwright to have it
upgraded. He asked me what would you have me do to it if your
not happy with the sound in general, I did read between the
lines at that juncture and let it go. But there are good
products out there that do benefit from upgrades.

Someone once said something along these lines: The sound quality of a given component is 75% due to the circuit design, i.e. the engineering, 75% due to component part selection, and 50% due to build quality.

I like this not just because it's funny but also because it reflects the truth that a given person can focus intently on just one of these aspects and can improve sound quality significantly and then conclude that this is the most important factor. For example, a designer might spend lots of time trying different operating points with his tube circuit, or a modder might spend lots of time trying different capacitors, or a builder could try different layouts and different chassis materials. Each one will find that some variations are better than others and there may be even be a "best." But this experience does not mean that this one approach (circuit design vs. component swapping vs. build quality) is the only or even the best road to good sound. They are all obviously very important, and none of them greatly outweighs the others in my opinion.

From the other posters' comments, it seems Frank Van Alstine is mostly in the circuit design camp, but I am sure that even he would acknowledge that component quality and build quality play some role in the sonics.

First you do the circuit design.

Next is to see how much it is affected by materials. Some areas in the circuit will be sensitive and other areas nearly immune.

3rd to to sort out what the best materials/parts are and install them.

4th- the 3 most important things in audio: listen, listen, listen.

Salectric, well said and spot on. It requires one to have an open mind and the desire to persue all these important aspects of a build and the resulting sound.

Atma, also well said as usual.