Does anyone know if, instead of having the remote stations grab the signal wirelessly, can I connect an ethernet cable to it so that it gets better signal?

I need to set up a network in a very large house, I plan on having the Airport Extreme as the main base and a couple of Airport Express to extend coverage throughout the house. The instructions on this page- http://support.apple.com/kb/HT4262?viewlocale=en_US - say that each remote station needs to be within wi-fi reach of the main station. That makes sense but I want to hard wire each remote station to the main station via ethernet. Does anyone know if this is possible or will I be stuck with wifi only?