How about using an L Shape configuration with 2 sofas, one facing the window, so that it creates a little hallway at the back. Include an occasional chair in the mix, so that you have some flexibility with seating.
How many people do you want to seat? Is that a walk through beside the stairs? Is there a view out the window? My first instinct is to say two sofas facing each other so everyone can see out the window and enjoy conversation.
Help transform long and dark family room
Help with long narrow living /dining room
Furnishing living room