No, light movers don't really give you more area, they give you evenness. They allow you to get the light closer to the plants without burning. A light mover and 1000 watter isn't going to cover a 4x8.
You will get more yeild with 2x1000 than 1x1000.
I've had tops 4" from a 1000 watt bare bulb without them burning because the light kept moving and I had a fan under it.
All that said, I don't have a problem with light movers. They have some uses and I would be happy to have one over my 4x4 moving 2 ft back and forth just for the benefit but I can't rig one in my current space.
They don't however double your light, despite what they hydro store says.
See my grow in the vertical section for a rather interesting use of a light mover with bare bulb.