No, when the sub comes it'll start playing the sounds that you've removed from the speakers set to small. It's better use of amp power, and speaker dynamic range to do things this way. There really should be no speakers set to large when playing movies.

For two channel music, you may want to use the M80s alone, but if you have the sub placed, and calibrated well there'll be no reason.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris