Just keep moving things around until you like it. Too many factors are involved so nobody can answer your question without taking all other aspects into consideration.
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I'm sure it depends on all the ingredients, but if you move your speakers far enough out from the back wall, you should minimize any negative impact.
In my case, when I had a 50 inch rear projection back and between my speakers, the only noticeable affect was that the soundstage was raised about 3 or 4 feet. Which I kinda' liked.
FWIW, my speakers were about 5.5 ft from the back wall to the front face of the speaker cabinet.