Keep in mind you should always use the native resolution of modern screens, or the image quality will suffer big time.
If you take acoustics into account there is not much choice you have with placing the screens ...
You'll end up around 80 to 100 cm viewing distance with a side by side dual screen setup.
One important factor that often gets overlooked is pixel size.
You can get 1920x1200 resolution in 22" format or in 27", both will display exactly the same amount of information, but the size of the fonts and UI elements will vary dramatically, for lack of a better wording.
Sit down with a pen and a piece of paper and compare the pixel sizes, it's basic geometry 101.
Oh, and be careful when putting another screen on the side, gotta push it way back or it will mess with your stereo image.
And finally, better make sure you can return a screen when buying, there are many that emit ugly humming noise from the PSU, even big brands, don't know about you, but this would drive me nuts in 5 minutes.