You may be opening a can of worms here, but here is my take on it....
For the first epoxy coat, it does not matter just use a good name brand. That is going to be your base and you are going to let that completely cure since you will do bodywork after.
After that, it mostly matters as you lay down the sealer, base, and clear if you do it in the recommended sequence before the previous coat fully cures. So, if you are going to seal, base, and clear back-to-back (like after flash etc.) they MUST be the same brand and compatible or else the chemistry will cause problems. This is not necessarily true if you let each layer cure, scuff, and continue. (oh man, some people are going to get on my case, I can feel it). So, the best advice is to just stay with one brand that has proven compatibility between layers. That way, you have your coating options wide open and the chance of a chemistry problem is eliminated.
But for the record, I have sprayed Nason base with a Kirker clear without long-term problems (my friends car). I just don't recommend it if you don't have to.
RGAZ