In my experience using a small monitor with X configured to use a virtual screen (i.e., the monitor just shows a small part of a much bigger desktop and you can scroll it with a mouse) is just as good as the giant monitors. I don't feel I really gained that much using 30" or 2x24" in comparison with the 15" monitor and 2000x2000 pixels virtual window I used to use in the past. Of course it's hard to argue that large monitors aren't nice, but I think the benefits for writing code are overstated.