Hey, cheers!
Maybe i should do a demo of the grossmann...I'm a bit more used to it now and how to mike properly inside the cab;tried different mics, different speakers (some of them weren't worn in, as i shot the vids, with no eq or filter or postproduction in most cases) and i'm still experimenting. I checked it with a vintage 30, g12k100, g12evh and a g12t75 with a sm57, 906 and with the sm7b. Single 57, single 906, or both. I have a few amps so there are much combinations possible, which doesn't make it easier =D
I got good results using the sm7b ( i bought it a few weeks ago as a vocal mic, originally) but i did no vid with the sm7, yet.
I guess peavey on post gain 3 is to loud for the small room inside the cab, though the lid and the cab is treated with resonance absorber. You find all the specs and some samples of the sg-box (open and closed) on the grossmann homepage.
I had exact the same thoughts like you now and i gave the grossmann a shot and i did'nt regret it. It's not a miked 412, in a treated room, but a very good (and relative silent) analog recording solution for a homestudio...And the speaker is frontloaded, which also makes a difference...