You know, there is a controversial topic i created on a version I Herbert somewhere on this forum, so my opinions about them are......open minded to put it nicely
But i do know that Evergrey uses Herbert's on their recordings, and that tone fits the heavier stuff great and also sounds amazing, under a mic you can pick up the complex attitude of a Herbert much better than live where i had the chance to hear one in a band (or not hear one in a band) environment against a JCM800 combo.
I can back up the Herbert I or II reference, that would be a great addition for what you are wanting, they have a complex attitude and thick is exactly how it could be dialed if you wanted
Funny thing about that -- the guy who has the demo amp just placed an order for two amps -- a Colossus and a brand new 3 channel rack amp called the Artemis. He tried to talk me into letting him keep the demo amp until he got his Colossus in a few weeks, just to tide him over. I told him "no can do" since you needed it!