In a nutshell, K100's are going to deliver the tone of the amp the best with as little coloring of the tone from the speaker's own characteristics as possible.
A speaker like the V30 is at the other end of the spectrum, it has a ton of it's own characteristics which are the super strong mids and presence. The K100's are darker and maybe a hair tighter, neutral sounding really does sum them up once you've tried different speakers.
Keep in mind that Peter Diezel tested and tuned the Herbert while using a cab with V30's, from my understanding.
I just a few hours ago pulled 2 V30's out of my Mesa cab and did the X pattern in my Diezel FL and the first 5 minutes of playing I could tell a noticeable difference, for the better. It gave the sound just a hair more crunch, but not over bearing like a 412 V30 cab can be that people complain about. Very crunchy yet I can still hear the smoothness and clarity of the two remaining 100's. The V30/K100 "X" is what I would go with if I were you.
