Airport Express & two Linksys WRT54Gs

I bought an Airport Express in hopes I could extend the range of my network (as well as print wirelessly and play music). Anyway, realizing that it would only link to my network, I bought another WRT54G linksys which I haven't been able to get to extend the range.

Does anyone know how I could put together a configuration to extend the range of my wireless network? As it is, the Airport Express is on the network and the main WRT54G broadcasts the wireless network. I have 3 older iBooks with Airport and want the range of the network to go beyond the current range by about 100-150 feet. Any ideas? I was thinking about getting rid of the two linksys routers and getting an Apple Airport base station.