i removed the Rear RCAs from the 4 channel amp.
im usin outpuit of the 4 channel and connected to the input of mono. and the subs work.
i have the front rca connected on the 4 channel but the speakers do not work. im amplifyin the rear speakers right now because I don't have front ones. So I guess i'm going to have to split the rear channel in the back of my head unit like x2o said.