I am looking for some thoughts especially if you have done this. I am thinking about adding a back speaker to my 5.1 but the issue is my 2 rears now are not moveable to the sides. Right now they are about 18"(to the grill) from the back wall pointed to the center listening position. This is about 4.5’ from the back wall in a 15” wide room. With these speakers where they are would it be worth the $700-$1000 investment to add the 6th speaker between them? If more info would help let me know. Thanks for your thoughts!