If you are crossing them over around 40Hz anyway for movies, my thought was that they were likely to be rolling off below there and would not contribute enough to the overall sound to create a "double bass" condition, and with the sub in the mix they'd be basically out of the way. It's entirely possible that this scheme would not sound as good as what you are doing currently, but if it did it would make the system less tedious to use when switching between the two modes.