Placement depends to some extent on what subs you are using. With the Vandersteen 2wq subs that I use, I need to keep them near each speaker as the subs reproduce frequencies high enough to affect imaging.
Move your sub
Caught an Art Dudley video about moving your sub(s) from behind, beside or between your speakers to the seat end of the room. I moved my REL back so they are in the same plane as the listening position. Much better! Try it.