Voodoo Lab

I'm getting back into completing my rack and had a question for the wise men and women on this forum!

Okay so I have an isp decimator pro rack g, sansamp psa-1, and g major 2 effects processor (all rack equipment) I've just setup and it sounds amazing to my ears.

Just wondering if I need a gcx and gcp or if a gcp can do everything I need to control the sansamp and g major?

What I want to achieve is 4 channels on the sansamp, (clean, rhythm 1, rhythm 2, lead) and the rest g major effects.

My questions may have been answered before but I haven't found anything relevant to my exact setup.

Thanks!