Hi,
80hz is the way to go.
I have a Mission speaker set up (M53 fronts, M31i rears, M7C2i front centre, M3C1i rear centre, MS10 sub) using the Denon 1906, and have set all speakers apart from the fronts to small.
This will allow, (correct me if i'm wrong), more bass to the sub and leave the rears to concentrate on effects, and the centre to deal with dialogue.
With the crossover on the 1906 set to 80hz, the sub delivers controlled bass which you can hear and feel without it being overblown.
Just my humble opinion, but worth a go I think.