I bought a house with four Sonance speakers built into one wall and the ceiling. I want to place a 120" screen in an archway between the room and a dining area but I'm having a problem with speaker placement (see pic) I'm thinking I'll place some JBL cabinets that I have on either side of the arch to serve as my main speakers but I'm new to this and don't have a real clue if this is ok. If I absolutely had to have a center speaker, could I put a very thin one along the back wall behind the dining table? The dining area is all windows and I figured the screen will serve to block out a lot of ambient light in the daytime in this position. Since I can't really move the wall/ceiling speakers, what's the best thing I can do here?