18’ is a generous size, so have you thought about splitting the room into two areas: one end for t v viewing and the other for visiting around the fireplace. I searched for back to back sofas. There are lots of arrangements for you to look at, but this one caught my eye. You could put the fireplace between the two windows with a great piece of art above it. Maybe even cover that section with some interesting wallpaper. TV goes at the other wall in a built-in.

can you post a pic from the other direction? (stand next to fireplace) can the round dining table be placed closest to the kitchen? maybe off to the right in the foreground of your first picture as shown in your floor plan? are you putting a tv in there? where is the cable outlet? this layout is rather long and narrow. media cabinet lay out do you have an area rug? I like something like this to the left of the fireplace under the window or behind the sofa along one of the walls something like this would look cool. easy to hack w/Ikea Billy Bookcases.

Creating 'flow' is all about coordination. That includes soft coverings (window coverings, pillows, floor coverings, etc). Your drapes are the beginning (and in this setting, the end) of the coordination effort. The two sofas in two different styles and two different colours create a hodge-podge sitting area. I would start with figuring out the style you wish to portray. Once you have that fixed, then figure out a colour scheme. After that, you will want to move ahead with the soft coverings. An area rug that compliments the drapes (you will want to get all three sets of drapes coordinated) will go a very long way. But first the big stuff: style. Either the orange modern sofa stays or it goes. Everything else appears to be traditional. The large brown sofa - being over stuffed - is in opposition to the orange sofa. It is 'over stuffed American kitsch'. You will need to choose between the two. That's where you start.

Instead of a sectional, you might consider doing a sofa and some chairs. It would make the layout easier to switch up and you would perhaps provide more comfortable seating for you and your loved ones. If you want a sectional though, you might consider looking into apartment sized sectionals. Included here are just a few images of our designs to aid you more with your current dilemma.