Triple Head Setup

Currently I have this kind of setup:



I have been happy with it, but since I have GeForce 6150 on the mother board I was thinking adding one more display so my setup would look like this:



After reading about multi screen setups it seems that it is currently impossible though. Supposing that I want to move my windows from screen to screen (xinerama/twinview) and have composite enabled. Please correct me if I'm wrong.