My living room layout is very similar! I had my couch horizontal in front of your window creating a entryway, maybe put a console table behind the couch.

Consider a grouping of four swivel chairs in front of the fireplace and a pair of upholstered benches at the two windows; game area in the corner if your bunch enjoy that kind of family time. I see a chain hanging from the ceiling which reminds me to ask about lighting. What kind of fixture lights the stairwell? If you ever want to add TV, consider enclosing the stairs with a pony wall pre-wired for TV on living side and for a pair of sconces on the stairs side. Here are some fun and comfy looking chairs. These are a bit more traditional; what's your style? One take on the pony wall idea.

Wow, this is tough because of the double doors! I think what you need to do is make two sitting spaces in your long living room. One sitting area will be in front of the TV and the other will surround the fireplace. The fireplace sitting area is a little tricky because of the doors. Here's how I would do it: I think I would position two chairs at an angle, facing each other, just in front of and on either side of the fireplace. The one to the right would be slotted in where the bookshelf is so that it doesn't interfere with the doors. You could also add a side table or two. So these two chairs, and the fireplace, would serve as a sort of conversation nook or reading area. Then, to make that configuration flow into the other sitting area better, flip your sectional to the opposite wall, and the cabinets to their opposite wall (you might need to separate the cabinets a bit--doesn't look like they'll fit, but they're modular yes?). You'll also need to push the sectional toward the wall with the door so that you have enough space between the two sitting areas. Also might want to add a sofa table along the back of the couch arm that would then be facing the fireplace sitting area, not because it's necessary but just because it could look nice/hide the back of the sofa. Instead of a sofa table, you could also do a cabinet, tall plants, a bench, what have you. That's what I would do if you wanted to keep your same furniture. Obviously lots of different options if you wanted to replace it, but however you do it I think two separate seating areas would be a really lovely use of space.

I do tend to run anti- sectional, mostly because I see posts where people are really struggling with the setup either before or they’ve brought it home. Also I surmise that it looks more current to a lot of people and also that it seems “ one and done”. That’s just my guess though. Plus not many people including lamps. However, I do think they work best for families with children, in that sort of square or rectangular space family room or media room with obvious TV wall ahead, and assuming of course that the space is big enough for pathways. Whereas in these open plans, with pathways may be on an angle & where you might be trying to focus on a fireplace and a TV, there’s a good chance that your furniture needs to be able to be angled and juxtaposed in different ways. So I agree with above comments that it LOOKS like a big sectional is not the best way to go in this space. To some extent comfort is another aspect and highly individual depending on who’s in the home, who visits, as well as the actual furniture construction you get.