I recently purchased a Dell U2410 for my new build and I am incredibly happy with it.
However, I have been thinking about adding a smaller second monitor as I am quite used to that set-up at work for accessing multiple windows at the same time.
I'm not looking for anything like the same size as my current monitor, nor the same quality as I will not be gaming or watching movies on it. I was thinking that a 17" 4:3 panel rotated to portrait would be perfect as it would be nearly the same height and pixel count of my main monitor.
I have a Dell 17'' that I occasionally use in conjunction with a wide screen dell 23'' and like you, I prefer a little different look for productivity reasons. I'd go for it if that is your preferred look.