You can do better than Chromecast with the Chromebox setup, you can share your screen, window, or document, into the hangout so that all participants can see it. You can do this now with Hangouts, you don't need the Chromebox.
We use this at Google for all of our video conferencing, and have for years. It's very well battle tested.
Edit: It looks like there's a $250/year fee per Chromebox. I'm not sure if that's good or bad compared to other vendors. You can connect from your computer or phone for free though.