My house is normal apartment just one wireless router should be all you need. I've used just one old-style (flat white square) Apple AirPort Extreme and it easily covers a 2500 square foot (250 m2) single-story 5000 square foot (500 m2) two-story or 7500 square foot (750 m2) three-story Home all by itself â€” presuming you put it in the middle of everything.
1. Connect your DSL or cable modem to your AirPort Express using the WAN Ethernet port.
2. Connect your AirPort Express to your home stereo or powered speakers.
3. Plug AirPort Express into the power outlet. There is no "on" switch.
4. Use AirPort Utility to create a new network. Ensure that "Enable AirPlay/AirTunes" is checked in the Music tab.
5. Open iTunes on your computer and choose the AirPort Express(es) you wish to stream music through from the speakers pop-up menu in the lower right-hand corner of the iTunes window.
How To create a wireless network with airport express?