I have a MkIII no stripe + and a Quad, which are both close enough in character to the IIC+ lead channel.
I haven't found anything that doesn't sound
GREAT through them. But I tend to venture most between '80s metal tones ranging from the original Bay Area Bangers (pioneering thrash, early Metallica, Slayer, Exodus) to the Sunset Strip sound (DeMartini) to NWOBHM (Maiden, Priest) and Jake E. Lee on with Ozzy and Badlands.
Anything along the lines of a Charvel San Dimas, Jackson Soloist, ESP Horizon or MIII or Eclipse with a Duncan Distortion/DiMarzio Evo 2/Bare Knuckle Nailbomb nails it. The Marks can get wooly with high gain, so clarity and edge are essential! DiMarzio makes my favorite passive neck pickups, especially the Air Norton and it's slightly mutated younger brother, the Liquifire. And the EMG 81 or 85 or 60 are simply fantastic with the subtle chorusing effect from the preamp, especially when you use 4x12s in stereo as I do. I can't decide which I like best, so I have variations of all of these.
If I had to pick one that makes me feel like I'm in God Mode, that would have to be a Jackson Soloist or equivalent with EMG 85 at the BRIDGE (highly underrated, but ask Steve Lukather about this concept) and just a touch of EMG SPC mid boost. The 81 is even more aggressive and the ultimate crunch pickup in my view, although not as full and satisfying for leads. So again, I have both. The 60 is EMG's best neck pickup for me.