Yes, a nice, extra 27 inches will do.
(Personally, I don't need an extra monitor. I use my 13 inch Air in the pub, on the train, at the coffee shop, on the sofa. I work the same way everywhere I go, so plugging in an extra monitor in the office just doesn't feel right.)
Also: we look at nothing else all day, so we might as well make this staring competition count.