chris_EIT,
RE: "Actually, when you say all 3 have very different tone I disagree slightly.". You then go on to show that Metallica and Petrucci have used Mark series amps and the fact that your Mark IV can achieve those tones as evidence that they don't have different tones. Sorry, but that really doesn't make your case very much. The Mark's are known for being very versatile amps, firstly, so the fact that two artists both use them in no way means that their tone will be the same. Plus, all it takes is merely listening to the artists in question to realize that their tones are not the same. With all that in mind, I'm not really sure what point you are trying to make.
If wicked wants truly useful advice, he still needs to clarify exactly what kind of tone changes he would like to make; only then would we, or he, know that the advice we are giving him is accurate to what he wants.