Place the sofa & loveseat that you have now in an L shape like the sectional would be and live with it for several days. That will help you get the feel for walking around it. Are you getting a rug? Window treatments? I would lower the TV to eye level when sitting and get a wider console (at least 25% wider than the TV).

Personally, I'd get two sofas. This will allow for an end table and lamp to be placed in the corner. Also, people usually like arms to lean on when they sit. However, if you like the extra seating the sectional offers, I would decorate the curved void with a large floor vase or floor lamp.

Here are multiple suggestions for dealing with your entire space so that it works for you. Budget friendly: --Avoid a loveseat as usually only one person sits on them and visuall take up a lot of room. You already have a dark brown sofa, so you want something lighter in chairs. --Instead get two comfortable arm chairs up on legs that will eventually coordinate with a rug you might think about getting to anchor your living room space--in a layout like this, or one chair facing window and one facing kitchen near a real coffee table to create a conversational grouping. I have a whole Ideabook of photos called "Brown Black Sofa Dilemmas" that show how to balance out bulky or dark sofas with light armchairs, coffee tables, rugs, art. This one shows a round coffee table with legs in same color as sofa. Not light pillow, rug. Less budget friendly sectional option if you sell the brown sofa: --Get a small scale (low arms and back but cushy) but very comfortable sectional in a camel color, not black or brown, and add one color coordinated chair like the ones in the above photos. Place the short end of the sectional facing the window and the long end where you have it already. What you're doing is creating a "path" from the doorway and another down the left side of the room. Place or resell your ladder display and maybe do some shelves around your TV for a gallery/art wall. Layout with sectional but you would only have one armchair. Note that if you could get a narrow console behind sofa (replace ladder as suggestion), you could put store small ottomans for group seating to pull out as needed)

If you can fit two sofas of full length, I think they offer more flexibility. You can move them into several different arrangements (across from eachother, L shapes). Personally I like to be able to have two adults lay down on sofas for watching movies so I would want both sofas to be long enough for that purpose. In rooms that can't fit two full sofas, sometimes a sectional will allow two adults to lay down, which I prefer over a sofa and a loveseat. But the sectional inherently limits how you can position the furniture because the components usually only fit one way and generally shouldn't be separated.