What Airport Products are Necessary?

Hi!
I have a Billion WirelessG ADSL modem/router and am already connected to it with my powerbook g4 - no hastles.

I have two imacs that i'd like to connect wirelessly and can't work out which products i do need from the airport range... As far as i know, they are not "Airport Ready"

I guess the question is: Do i need the base station, or can i just buy an Airport card? Or is there a usb wireless receiver that i can use?

The Apple Store give up no information to help me... It is VERY ambiguous and aimed at making me buy EVERYTHING with the airport name...

Any advice would be appreciated...
Ta

If you you already have a wireless neiwork setup. Then you will need to get wireless network cards for the iMacs.