I am running SLI 670s OCed to 680 speeds. I am using a 1440p monitor and have my old 1080p monitor as well. What kind of performance hit can I expect if I connect my 1080p monitor to use for static things like chat or a web browser while gaming on the 1440p main display?
Not much at all. Displaying that kind of stuff barely registers on a graphics system like that.
You'd probably experience a 1-2 FPS decrease.