It is great to build very high quality audio amplifiers! But...that quality can be ruined by the speaker attached to the amp. So while this article is a welcome reminder about the importance of component selection, don't over-design the amp and under-design the speaker. And make sure the supply noise is not a contributor.
Oh, and the overall gain that is required will dictate what the noise performance of the amp stages should be.
Many applications simply do not require the ultra-low noise performance. The high performance is needed in the professional audio, recording, and measurement industries, and also for the audiophiles among us.
The final graph is very dramatic, and a salutary reminder to do one's calculations. However to dissipate 0.3w in a 1K resistor would require 24v RMS, which is typical of a power amp rather than a low level circuit. In a low level circuit with output of 1v RMS and R2 =2k2 the stabilised resistance change would be 3ppm for the bulk resistor and 0.5ppm for thin film.
Many audio circuit designers seem to ignore the fact that, with regard to noise, all resistors are the same EXCEPT when DC flows through them - which, of course, causes the "excess noise". Most applications of resistors in audio circuits see no DC, yet many audiophiles believe that an expensive resistor will result in lower noise. Of course, low excess noise resistors are useful in applications where there DC does flow - the plate load resistors in vacuum-tube circuits, for example. This article seems to underplay that fact.