My solution to getting a huge sound really does not have much to do with the amp or cab. It has not been helped by the advanced settings or any of the basic amp settings as well as any EQing. These all shape the basic tone wether it be warm, fat, punchy, harmonically rich, bright etc. To get a huge sound i usually use a side chain of dual delay into a stereo reverb to the output and another side chain with yet ANOTHER reverb also in stereo to the output. The 3rd path is the dry signal from the cab or post cab EQ. I then mix all these meticulously and get huge spacial sounds which are actually very clear and crisp and not muddied. I usually will select the different verbs to get this effect like medium hall after delay and the other verb would be the medium or large plate.
Most importantly i usually go back and turn down the gain, turn down the input trim, down on dampening, down on transformer match, down on base etc. I find i need very little drive but usually max the master on many of the non master volume amps. My tone is best described as slightly past the edge of breakup but with the delays and verbs the sound is gigantic. This approach may not be best for recording since you are "locked-in". May not be best for live use since every venue is different.
For me the most important problem i have encountered is that one you get into the time based effects, the basic tone changes and has to be reworked to better suit the use of the effects.