Do yourself a huge favor here. Get some grid paper, and draw it to scale. Two squares equals a foot, or five squares equals a foot. Then take very real measurements of the sectional and sofas you have in mind. Take measurements between the window/sliding glass door. Take exact measurements of the length of the media wall. If you don't have a particular sectional or sofa in mind, pick one out that you like, and measure that. This is what I do as a decorator. Real measurements, real scale. Measure every single bit of the wall. Measure doorways and entrances. I promise it isn't too difficult!

I agree with The Organizing Decorator. In our profession too, meticulosity goes a long way. It helps a lot when figuring things like this out too.