I believe there are splitters, but then you would be showing EXACTLY the same image on the two monitors that were split from the same output, so what's the point?
You'd have to get another video card if you want a third monitor. Two cards won't allow you to use all three as a single screen though, you'd only get three separate screens (A main screen and two extended screens).
I imagine you could get a cheap $30 HD6000 card (HD6450 1GB) or similar for that third screen and continue gaming with the GTX 560 on the single screen.
Sounds like more hassle than its worth though.
Screens aren't too expensive, why not buy a single 22" 1920x1080 screen for $160 and add another 4x3 screen but disable it unless used?