I tried it like that on my 19" monitor (exact same clone dimensions I think) and hated it - windows way to small. So i decided to also use the other 19" monitor which I was going to use for web browsing and other tasks.

To run all 5 instance in one screen I think at least a 22" monitor is needed.

As for single-boxing, I run 1440x900, but windowed mode ... the frame around doesn't bother me.