Attempting rear speaker connection wiring

[pixster-S]

When attempting to connect rear speakers to my HAES amp (986 Cabrio M490) Harman 49134 70313/01, not clear which are dedicated to the rear channel. Even on complete rear fade, the ones directed by wiring diagram don't produce same "punch" and clarity as those driving the front sets? Any thoughts? Are the front sets to be by default the dominant pairs? Thanks.