Separate pieces will give you more decor options than a sectional. Who would want to be limited to very few decor options?! Maybe instead of a love seat/couch, you need a love seat and two/three low profile upholstered chairs. (Measure twice, buy once!) For my living room, I wrote a floor plan and cut out pieces of paper that measured my potential furniture. That way I could move them around and see what might be the best fit. Experiment is the key! Since you have an octagon, think of it as an oval shape, and embrace your oval. Draw out your elongated octagon. Put the fireplace at one end and your windows at the other. Draw in your doors as well. Be sure to consider your traffic flow. Make sure people can move around freely. Pick an inspiration piece such as a favorite piece of fabric or accessory. Can't wait to see the result!