Here's my idea in response to your post:
If you're starting from scratch on furniture, I would put a large L-shaped sectional or sofa with chaise unit along that one long uninterrupted wall (to the right of the entrance.) That way, you can put a media cabinet and TV along the opposite wall. You'll have a decent angle on the TV and enough of a thoroughfare for getting to the sun room, but because of the L-shape, the sofa will still relate to the fireplace. A round coffee table further help the sofa to relate to both fireplace and TV wall.
Here's a 5-second sketch:
|Snazzier. But not to scale-- I'm not that fancy.|
If you already own a non-L-shape sofa, what about floating it on an angle opposite the fireplace? You could put a desk, low bookshelf or nice console table behind it to make the "floating" quality less awkward, as well as increase surface and storage space.