Not to quibble. But to quibble.
I don't think that is wholly accurate Intel. GEQ and Tonestack is an apples
and oranges conversation. I'd never equate the two.
GEQ is post distortion/preamp.... so it acts differently than any kind of active or passive "tonestack"
on other tube amps.
And I do think that the GEQ can become a crutch. Lots of players leave it on by default and forget that
there is also a GREAT Mark-series amp with a lot of tonal options available BEFORE you get to post-distortion
by using the amp's tonestack in the preamp.
That was my only point. You don't have to assume it needs to be "On" and used in the standard V config.
There are many ways to use the GEQ---often as you would in post-production, or by micing an amp and
then using channel strips, EQs, and Mic Pres to further sculpt the sound. It can be dramatic. It can also be
subtle. 90% of Mark users, I would contend, forget about the subtle aspects... or leaving it "OFF,"... and
fail to discover all the other great tones in those amps that are right at their fingertips, too.