With M2's I think I would try a higher crossover, probably 100 to 120. But it all depends on how it sounds.
I agree. I think it would be worthwhile to try a higher crossover point other than 80hz with the M2. I don't know if I would go as high as 120 though. As to the dynamic range and power handling of the M2 for home theatre, their capabilities are dependent/limited on room size and listening distance. They would be adequate to use in a small to medium sized room at reference levels powered by a receiver.
