Thanks for the ongoing suggestions and input.
The Kingmaker definitely sounds Black-Metal-worthy, but I'm not quite hearing the characterstic HM-2 "growl" in that clip (though this may be my dinky phone speakers coloring things).
Are there any links to and/or clips for that Damnation Audio EQ? I was unable to find any via Google and site searches here.
I never thought to cascade an HM-2 and muff back when I owned both, which, no doubt, sounds gnarly as a mofo (on guitar as well as bass).
Maxon Water with boosting plus Channel 1 of my Boss GL-100 will probably be a short-term solution for the time being. I plan to also explore new para EQ options added in the latest Zoom MS-70CDR firmware and to dust off my Atomic Amplifire soon (which has the option of at least 3 parametric EQs positioned anywhere in the signal chain).
If the correct EQ curve can be achieved, the next frankenfuzz hybrid will be Bee Baa with HM-2 grind.