I use a separate system for video - different amp hooked to an AV preamp (Marantz) and I just switch over the speaker cables from one power amp to the other when I want to switch from audio listening to video or vice versa - I suppose one might be able to find some sort of switch that would do it, but not sure that it would be sonically neutral.
I use a separate multichannel power amp for the surround channels.
I use a separate multichannel power amp for the surround channels.