Do you know if your neck strain is due to horizontal or vertical movements? On a few times I had to work with big monitors (>30"), I noticed that I placed/sized windows only at the center, and not all the way to the top. Looking up too much is not comfortable for my neck. For the horizontal movement, I have no problem. But when my eyes are focused on the centre part, if I need to look at the extreme left/right, I need to refocus, which is slow/tiring.

My work setup is 2x24" monitors, and I really prefer 2 small ones instead of a bigger one. I can orient them so that all pixels are approximately at the same distance to my eyes.