Buy another router? You can get access points that connect to the Router and merely extend the range. You could also try range extenders...little things you plug into unused wall sockets to increase range.
Having multiple routers around would be difficult. What you need is access points. You can get two cheap Belkin54g access point/routers from Wal-Mart (ughhhhhhhhhhhhh!!!!😱) Just make sure to configure them for access point mode only.