I used to think you had to have that middle "free space" but I found it all depends on what type of speakers you use...I have the "fireplace in the middle" issue and having moved my current speakers (Silverline Preludes) all over the room I finally realized they're fine about 8 inches from the sides of the fireplace and protruding straight 4 or 5 inches out in front of it...nearly 2 feet from the front wall. Any reflections are completely a non issue, imaging is excellent, etc...I have a little REL sub behind one of the speakers taking full use of the bass reinforcement of the small corner. Plus, I can look at the propane fake fire while I listen. The listening sweet spot is on a couch 3 feet or so from the back wall and about 9 feet from the speaker baffles.