Re: NAD JSX head
The red channel on the Vypyr JSX Model sound very close to the how Crunch channel on my XXX did. The Ultra Channel on a JSX is basically the same circuitry as the Crunch channel on a XXX. The differences being stock EL34's in the JSX, and the extra tone shaping controls the JSX has. Fat swithces, resonance, presence, etc. Peavey still sells the JSX, it's just rebranded as the XXX II, And the XXX is now the called 3120.
That being said, the vypyr JSX model is great, it models the gain structure and active EQ quite well. The same can't be said for the vypyr XXX model IMO. It's more marshally, not as modern sounding. The JSX is an awesome amp that's super versatile.