If you're crossed over at 40Hz, wouldn't you get less punch compared to crossed at 80Hz since 50-70Hz will be played mostly by the M80s instead of the sub?
That punch is lost when going through a linear sub as it is really designed to play lower than that, well some subs play that range very well, the PB12-nsd comes to mind, but it had a different feel to it than the M80s bring and the PB12 also had a hump in its FR right in that 50-70hz range which is why it had the punchy sound.
The M80s crossed at 40 are right in their prime bass range. I set them to small so my PB13 can work on what it does best, really low notes. I also found that during movies the sub is so busy hitting those low notes that the punch of gunfire etc. has much less impact with the higher crossover points. I am also sure alot of what I have found is room dependent, so YMMV. However, a better upper bass is the main reason I went from M22's to M80s, their ability to play that mid bass with more authority.
