arduino xbee network

hi all,

i need to sent from one computer control signals to to multiple standalone units. each unit needs to control 4 servos, and they are each ~50m apart..

at first i though about using RF links in the following way: transmit using one TX (using laptop+arduino+RF/TX). then, each unit will have: arduino+servos+RF/RX. the things is that the signal is too weak to transmit the control command fast and reliable (using the virutal-wire library).

unless someone have some tricks how to boost up the signal somehow, i'm thinking about using xbee modules instead, forming some network maybe. anyway - as i never used these modules - any suggestions as the best way to accomplish that are welcome. thanks!