Dear Todd, I am aware that I am a bit late to the party but nothing like some self education during the Lockdown.
I have the A870 connected to the following as 5.1.2 ( but no sub)
LR -Floor Standing - B&W 603s 2019 - Set to Large from MLP - Distance 13.6 Feet
C- B&W HTM6 - Set to Small @ 60...