Just to be clear (since you reference both) the Airport Extreme Base Station doesn't support AirTunes (it does however support external hard drives, printing, using a powered USB hub to more of either or both, and 802.11n).
The Airport Express on the other hand has AirTunes, can support a single printer, and is significantly cheaper. No 802.11n, shared drives, and only one printer though.
It sounds like you are after the Airport Express, I just wanted to clarify since you mention both.