If your brown couch is facing a TV then you have the best layout. Your rug should be fine for a sectional. When you get the sectional keep it as far away from the drapes as possible. AND for now , pull your brown couch a bit out from the wall and the chaise away from the curtains. If you don't have a TV on that wall, you could try the brown couch in front of the curtains facing the FP and then the chaise facing the brown couch . Put the end table as a coffee table between the two of them.

I agree with keeping the sectional away from the drapes, but be sure not to block that beautiful partition fireplace at the same time!

After getting the sectional and re-assessing the space, the next step would be to get a good coffee table. We have a few oval ones that may do the trick while still allowing the space to flow.
(My suggestion is the Oval Tulip Coffee Table in Calacatta Gold)

You can also include a lighter armchair or lounge chair to the side of the sectional. For the walls, you can opt for a mirror to brighten and widen the space, or a nice piece of artwork. In general, I would brighten up the area by choosing accents that are lighter in color compared to the rug. Hope this helps!

Thank you all for the advise. I love the coffee table idea for sure.