Preamp arrangement question

I recently added a Rotel RMB-1075 multi-channel amp to my RSX-1057 to increase output in each channel driven from 75 watts to 120 into 8 ohms/20hz to 20khz. What happens to the amplifiers inside the RSX-1057 receiver? Do they know to turn off or do they remain on and contribute to the overall output? Am I actually putting out 120 watts/channel + 75 watts/channel? If not and they remain on, what happens to the current they are producing? The owners manual does not address this. All of the interconnects are properly installed and the loudspeaker wires are now connected to the amp outputs. Just curious what is actually going on inside the AVR with this arrangement. Many thanks.