I've owned a Mark III (no stripe) and now owning Mark IV and Triaxis. The latter is advertised as the one containing, particularly, Mark IIC+ and Mark IV sounds.
Well, first, to achive the big guys sound (Metallica's, Dream Theater's etc) with either of them you must consider the nuanses as cab, mic (the number and combination of those), room, guitar, pups.
Each of the listed above amps has its own brilliance, but what you wanna start experimenting with is EQing out the mids using a multiband graphic. Even though the Mark amps are equipped with one, you still might find something interesting further on.
The second advise is go to YouTube, search for "Mesa Mark IV" and you'll get a bunch of videos of ordinary guys demonstrating the raw sound of the amps in their bedrooms, with out any studio tricks layed on.