Since your situation is already compromised and aesthetics are important to your wife, just do a TV and slim LCR soundbar if you need to place the TV over the fireplace. There are many nice options, I like Triad.
My wife and I built our home a few years ago, and I made sure I had input in the design of the great room. I don't know why American home builders insist on forcing fireplaces as a focal point down our throats. It's an unneccesary decorative fixed bulky piece of furniture, and we have to completely work around it in what is typically the most used room in the house. Our builder as well as the interior design people looked at me like I was crazy when I told them to move the fireplace to a different wall, as we started with a similar layout to yours. In the end we put a 70" TV on a nice custom media stand on the preferred wall, and did a direct vent fireplace on an interior wall shared with the garage. We got an L-shaped sofa such that we can sit on one side to watch TV, and the other side to just hang out by the fireplace and have a drink/coffee. Like I told the designer, I watch fireplace once a year at Christmas, and I watch TV every day.
I bring this up because you have 16' of room width. Why not put the TV and speakers of your choice on the long wall? In addition to better options for display and speaker placement, you can see the TV from the adjoining room.
You may not think you're going to use this room much, but that could change as you settle in. We have a dedicated theater room with soundproofing, acoustical treatments, the whole bit, but still spend vastly more time in our great room which is open to the kitchen and rest of the main floor.