Start with drawing a scaled floor plan in order to come up various options for furniture layout ideas.

I agree with Dytecture that a scale floor plan will be your best bet. You can use the Icovia planner here: http://roomandboard.icovia.com/icovia.aspx

It allows you to create a room to your own dimensions, add windows and doors, and to adjust the sizes of the furniture pieces you place in the room.

Also, for aesthetics and comfort, you really need to get the furniture off the walls. Find a way to float your seating in the space. You might leave seating on the wall where the red couches are now and float the rest around it.

An area rug will help to define the conversation area. Get one that's large enough to put the front feet of all your furniture on it.