Sixcess is a d6-based Attribute + Skill system
So crunch, or any maths-y mechanics will probably not be the thing players remember rules-wise of a session built on Sixcess.
Maybe it's Skills, Powers or Abilities – only playing may solve this mystery :-)
I'll have to pose this question to some of my play-testers and see what they say. The only math needed in Sixcess is to count your Sixcesses (the dice that come up equal to or higher than the Target Number), and the Damage resolution. The Damage throws some people, but I'm working on a gadget for the non-maths people. The interesting thing for me about Sixcess' Damage Codes and Armor Ratings, however, is that they dovetail nicely into the Size/Scaling mechanic, which allows for things like Damage resolution between a massive object and a man-sized attack. Anything is possible!