HAI Hi-Fi 2 network source

I have a Hi-Fi 2 4 source setup and testing it out. Right away I have a (I hope) simple question regarding sources.
 
I know sources should be connected via the 3.5 mm inputs either on the unit itself or RIM. I would like to be able to play music from the network- either itunes items on a PC or a mobile device. What is the best way to do this? Will connecting a Google cast audio device or AirPort base do the trick? Or is there something else?
 
I downloaded the app for the Hi Fi but so far it appears to do nothing.
 
I plan on using an Omni LTe and have this already but not all installed yet. So looking for an option now. If any one has done this already please let me know what you did, and if it can be done.

You can connect any device that has audio out as a source. Sonos or Echo for example.

This was way easier than I thought it would be. Bought a $30 Google Chromecast Audio, plugged it in. Now can stream from anywhere via the network (I typically use Spotify) and use voice via Google Home to do it all. Great so far.