My Sony amp has an 'on (tv) screen menu' to make nearly all the settings. Easy to find and work with.
Today, I was reading some of the paper manual that came with it and it mentioned there is also a set-up menu on the amp's front panel display. I had never looked at that part of the manual because the amp replaced another Sony amp that was identical except the old one was 7.1...this one is 5.1
Anyway, everything on the amp menu looked good until I came to 'speaker pattern'.
8 diff choices from 2.0 to 5.1......my setting was at 5.0

(prob factory setting)
Switched it to 5.1 and there was an immediate sound difference (for the good)
I should have read that section in the manual when I first set it up.....live and learn.