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monoblock is a single channel amp, hence "mono". they are used to run subwoofers.
4 channel for 4 speakers
3 channel for 2 speakers and a sub
2 channel for 2 speakers.
there are other combinations possible, but that list is keeping it simple, easy.
Can you use a bridgeable amp as a mono block
I doubt that your sub is 1200 watt RMS, to provide you with a amp model to run that sub we need the RMS value of the sub. What model sub is it?