Yes, you can stream music from any computer on your network to your receiver via the apple airport+the cable I'm including. Transfers will be in digital domain with this type of cable.
Sound is much cleaner via this input. Plus, it's really nice to have music streamed wirelessly.
FWIW, this base can also be used as a router, or printer hub for your network, or wireless extender. Not sure how many of those things can be done at once. May only have the choice of doing one, or a couple. Never bothered with any of the other functions since I just bought it to stream music into my living room.