For the most part with any projector in the price range you looking at going any larger than 120" would cause the pixels to become much more noticeable.
Most good projectors that can do an image larger than that cost closer to $2000+
Any inexpensive modifications to the lens by adding another would result in a brightness hit and would cause distortion around the outside edges.
Most good projectors that can do an image larger than that cost closer to $2000+
Any inexpensive modifications to the lens by adding another would result in a brightness hit and would cause distortion around the outside edges.