I'm assuming you meant a similar set up to this?
Trying to find a picture of what I wrote above, but googlefoo isn't working for me tonight.
But will try explaining it with reference to pic one.
Having the wall mounted speakers behind you angled down and at the back of your head would imo give more depth of sound, as having the wall mounted side speakers flat and in line with you would be just throwing the sound left to right.
From my experience only, I prefer a set up more like this:
Disregard the second image in the two part split, and the additional wall mounted front speakers in pic one.
Over 9,000 edits later I thing this makes sense but I can't brain today.