My usual strong preference for rooms that are meant to be lived in is to plan them to serve us in a variety of ways, and floating a couch in the middle of a normal-size room focused only on a TV, its back to...nothing, is so limited. Doesn't matter how many people have been doing this, there's more to family living than watching TV and a living room needs to accommodate other activities. Like chatting quietly with a friend, sitting together or on the phone. Organizing a club project. Building a dinosaur while dad keeps an eye on the TV. If it were mine, I'd sell the entertainment system and probably put a couch on that end wall, consider reconfiguring the sectional so the short piece backed to the wide top doorway, but the long stretch facing out into the room. Flat screen TV on the short wall in the lower left corner (happily hidden from entry too). Easy chair, or even two, in the middle (swiveling?). A secondary conversation area (chairs or chair and loveseat) by the fireplace. Or a reading corner and in the other perhaps a small card/games/project table or a desk and chair (facing out into the room). All open and sociable. The idea for a backless sofa is also an extremely nice one, but with the combination of a normal-size room and all those doorways/fireplace I would personally definitely pass on two full sofas with backs and otherwise keep the arrangements nicely open to each other for active living. (No neck strain from trying to admire the dinosaur without getting up.)

Napoleon makes OK fireplaces, but their efficiencies are terrible. The P4 Energuide efficiencies of their Luxuria Series of linears range from a low of 38.8% to 52.5% Which means that in the case of the LV38N 61% of the gas you pay for is wasted and the best LV74N almost half is wasted. The Valor Linears range from 66 to 70% P4 Energuide efficiencies. The Heat Shift allows TVs and other heat sensitive items above the fireplace as well as combustible wall materials up to the fireplace opening. Here is the Heat Shift Video.

We have the same basic layout and we mounted the TV to the side wall and used a swing-out to aim the TV toward the sitting area. You will never get the optimum mounting height if you place the TV above the fireplace with mantle and that is the most important thing for comfort. Out fireplace is 65" and the TV is 55" (soon to be replaced).

This often comes up on houzz; I’m wondering if anyone likes their tv at that height in a room that is approximately this size. I have a similar set-up in my soon-to-be new home, so I will be following you. The builder placed the tv outlet above the fireplace (not a low profile, in my case.) It would be much easier to arrange the furniture if I went with what was intended...but I, too, am worried about the angle for comfortable viewing. Not sure I would like to see a tv that is angled downward, and I agree with your concern about using the style that must be pulled forward and downward. I hope we both find a solution! Good luck in your new home. I’m envious of your windows!