That's a really nice setup. I like the way you've positioned the base units.

> ergotron stands that mounts to the back of the desk

I'll echo Xzin's comments on these things. I've just set up a four monitor "free standing" unit and it's really, really well engineered

Pre-purchase, I had quite a few discussions with my wife about how a stand with such a small footprint (which is essential for my setup - I'll post pictures when I finally get it all done!!) could possibly hold four screens securely.

I admit I had concerns too, but having actually put one together now, I have no hesitation in recommending them.