Suggestions on triple monitor setup

I've been working with dual screens for a while, and thinking about adding a third. Currently have a pair of 23 inch widescreen monitors, and would like a smaller third monitor either in the middle or off to one side to keep email and instant messages on all the time. It can even be vertical if I need to save space. I've got a cabinet I've set up for a standing desk, and have 50" in width to work with, and about 30" in height, so width is more of a concern. I can't just use my laptop screen since the docking station takes up too much space, and I have it docked on a lower shelf instead.

Something like this, but mount the center one below the other two, and it could be a 15-17 inch.