Oh, dont get me wrong, its completely unnecessary but that's why its called Xtreme Systems.
So if you're looking at the case from the front all you'll be looking at is two 560's side-on, blowing air from front (1st rad/front of case) to back (2nd rad/back of case).
You could have additional 4x140 fans joining the two rads. It would be quite the monster. I'm only saying this as you're looking to get a second 560 and it would give you a cleaner look if you concentrated the rads in one particular area. Otherwise it stops looking like an X2000. Just an idea, see how you go.