If you are planning to use your newly updated and changed version of Raspbian for all your other RPIs then you need to clone the SD card. There is a very good link which explains how to do it for windows. It is slightly needs more clicks than mac i suppose but the link explains it very well.

http://computers.tutsplus.com/articles/how-to-clone-your-raspberry-pi-sd-cards-with-windows--mac-59294