For crushing high gain, extreme is the way to go. 90 watts, plenty of output volume, gain around 1-2, master 11, treble 3, mids to taste, bass up to where it gets flubby.
Extreme can sound dry when you switch from Mark IV mode (i.e, Mark IV mode sounds more saturated). Lately I've been getting a better hang of extreme and how to make it sound saturated. First, you can turn the presence up higher on this than on Mark IV mode. Presence high on Mark IV makes it sound thin, but on extreme mode (at, say, 2) it adds sizzle and sounds more saturated. Secondly, play around with triode the variac switch. These tend to add some saturation and brownness to the sound, but at the expense of punchiness. So, find the optimal balance.
With the output at 11, using my combo and thiele cab, with these settings, I get a huge thump in the chest with each downstroke.