Thats what I usally do, but from time to time, I use both monitors. If I GM or have to write something, it's nice to have my sources and stuff on one display and my actual work on the other.
Current setup: i7-3770k, 980styx, 280g SSD, 1tb harddrive.
My current display is a Iiyama prolite e2481hs,
Its just for a simple dual setup, nothing fancy