Could be wrong and someone here could explain the 'tech' behind it. But an inelegant explanation as I have understood inmpedence.
When you see an 'inpedence' switch on a receiver, - beware. Be careful not to overpush the unit. The switch is there to protect the recievers amps from overheating and overextending itself, (and overheating all your internals) so the unit won't blow up and go into protect mode or fry.

When you have plenty of power (200 x 1) beyond reasonable spec checking on needed watts vs Speaker sensititivity etc. This switch is not necssary to protect your amplifaction from over extending itself. And particuarly with monoblocks your heat dispatation hopefully (depending on your metod of stacking) would not endanger the 'pre' part of your system.