New to computer audio and simple question....

I just purchased a Bel Canto 300i Int amp with built in 24/96 USB Dac. I am using this as a second system driving some smaller floor standing speakers. I have an Apple iMac computer in another room (about 30 feet away on the same floor)loaded with itune songs. I want to somehow have my iMac computer loaded with itune songs feed my Bel Canto USB dac wireless. I know I need to purchase some kind of unit that will make this possible. What do I need?

I don't want to spend anymore than $300-$400 new or used. Like to spend less really, but want good sound. I know this may seem like a dumb question, but this is my first attempt into computer based audio. My wife would also like to play Pandora and other such digital stations...