I have a 97 montero and I want to add a monoblock amp to power subwoofers. Now normally this would be done by connecting the amp to the rca's on the hu. but those 2 rcas have plugs that split to a green, gray, purple and white then those get plugged into a mitah cable that runs to the infinity. How Would I be able to use both the infinity amp and run a monoblock for subs?