Cam, if you run through the receiver calibration, it will figure all that out for you. The settings are room-dependent.

If you want to do it manually, set it to Large and forget about it. With Large, you don't need to set the cross-over because the entire content of the center channel signal will be sent to the 180.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated