2008 A6 brake pads question

Hi, guys, I want to replace my 2008 A6 rear brake pads from audi genuine one to StopTech brake pads and I want to keep using the old audi genuine front pads, but I am not sure I can do this, because I am worried about using two brands' brake pads on my car may have some bad influence on the quatrro system and the brake system, like ABS or ESP. Should I do this or just buy a new audi genuine rear brake pads and forget the StopTech? Any input would be appreciated!!