For the last ten years it's been a latte brown/grey, okay greige, 3 seater. I'm loathed to get rid of it as it still is so comfy, though somewhat worn and faded. Desperately trying to the find a drill, cotton or linen in a bright teal/ kingfisher/ peacock blue to re-cover. Something like this...

Find an area rug you love for the space in front of the TV, and pick one of the colours from that for a sofa to sit opposite the TV. Then go with a darker or lighter shade of that colour for a pair of armchairs to sit at the window end of the room. Add some scatter cushions and throws in solids and patterns based on the other colours in the rug for a pop and it should all come together in a cohesive look. Flanking the sofa with a pair of side tables with lamps on would also look great.

2 sofas look great when you are needed extra seating for people but i really like the armchair /wingchair idea with a sofa. As you have chosen a modern take on deco i would look at a side table that encumpases that style but as said functionality is key. No good having one sofa if you have 5 guests. It sounds so beautiful so keep moving with your ideas and remember that sometimes ideas can change with different advise but you have to love it

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.