Lighting a couch for digital replacement

king sized white sheet, 2 speedlights with umbrellas

Yup, just plain white.

Ryan I have a 4 head setup and I'm twenty minutes down the road from you. I like mexican food.

If Ryan wants me "on" the couch I should probably be the one buying lunch. Possibly a new lens for him too.

move the couch several feet from the wall and put two speedlights  behind it (to light the wall) light the couch with the other two. you'll get some light falloff but it'll be at a place easy to paint over in post.

Based on the information and what you're trying to do, all you need is the sunny day and the blinds open.  You will have plenty of light to evenly light the couch, you won't have shadows, and the right exposure will render the wall white... because it is.  Therefore, I would suggest that maybe this is being a little over-thought.  You have the lighting, the couch, and the camera.  Maybe take one or two shots bracketed over the 'correct' exposure and see if that helps.  Really, if the wall is evenly lit enough from the windows, you could probably do a color selection in PS and remove it completely and replace it with a white color fill.  That would really make it easy I would think.

Travis