My Mini has an external drive to hold the music and runs a set of speakers from the 3.5 outlet. It also runs a second set of speakers on an Airport Express. I just plugged in a set of speakers to my Airport Extreme through the USB slot using a USB/3.5 adapter. iTunes sees everything but the new speakers. The Extreme works OK otherwise as it runs the house WIFI. If I have to, I'll just get another Express if I can run multiple Extremes. I'm running 10.5.8 on an older Mini.