I have an Ibanez RG 7 string and I use CH3 IIC+ mode in Bright with the Treble and Mid at 12:00 and the Bass at about 9:30. The Presence and Gain at about 1:30 and the GEQ in the “V”, of course.
This was similar to the sound on Dark Eternal Night (Dream Theater).
BUT!,...
Not until I lowered the action on the top side of the bridge (the lower 2 or 3 strings, BEA) so that they “rattle” somewhat. Of course, you have to “attack” the string somewhat. The rattle, with some distortion (not a ton of distortion, notice the gain is just past 12:00), seems to create some of those higher harmonics. I actually found that more gain starts to “smooth” out the “growl” at the start of the note (while the string is still rattling) and it doesn’t sound as good.
I would even say, IMO, that the string buzz is more important than the amp settings for the type of growl I am referring to as is creates those higher harmonics. When I received the guitar from Sweetwater, the action was actually nice, but almost no buzz at all on the low strings and it just sounded flubby. So, again the rattle was a big discovery for me.
I am not pro and who knows what else the pros do on the albums but this got me close enough to be satisfied with the sound.