Yes the surround speakers will be missing from everything so you would need to re-enable them for movies.
Just going through the sound modes on my Onkyo and there is one called 'Theater-Dimensional', shows as 'T-D' on the front panel and the output is 3.1. I don't know if this is an Onkyo only mode, but maybe the Denon has something similar.
Denon AVR-X6400H,Sony KDL50W829 ,Virgin Media V Box HD, WDTV, PS3, Philips DVP9560, Marantz CD67, BK Monolith Plus x 2, KEF TDM 23C,23F & 34DS, Jamo D500, Darbee Darblet, Belkin F9G6223uk3M, Buttkicker LFE kit, IsoAcoustics L8R430, Mede8er 800X3D, Behringer B1200d, AC Infinity Aircom T9
Last edited by Dolus; 12-31-2017 at 07:12 AM.