I must have at least 8 years listening to 7.1 Trifield. I started out with 5.1 Trifield but found adding the sides a significant improvement. Sides and rears are subtle enough that you don't sense they are playing. Turn them off and you immediately notice they are gone! Trifield sides and rears add ambience to a recording from where it should be coming from instead of all the recording ambience from the front of a soundstage. The subtle nature of the ambient field coming from the sides and rears is a good approximation of real ambience.

mw