Can you stream to AX set up as a MAIN base?

[DudeDah]

so I have three airport express base stations. One serving as the MAIN base station hooked to the cable modem and two more to extend range and, more importantly, enable iTunes streaming to other parts of the house. Those two are working and streaming well. I just hooked up a set of speakers to attach to the MAIN base station but it doesn't show as an available base station in iTunes. So, I launch the Airport admin utility and it does not have the "music" tab for the main base station. Are MAIN base stations not available for Air Tunes? PLEASE HELP!!