I own a Roku, and find it works great when you're laying down on your bed and want to watch a movie on Amazon/Netflix. However, for entertaining, the easy access to Google Play Music and the ability to cast Chrome tabs was the reason that I chose Chromecasts everywhere, and stuck with the Roku just where I want to watch Amazon movies.
I haven't tried it before but it seems the Roku app on iOS lets you stream music to the Roku player. In addition to that, many new home surround sound systems come with Bluetooth streaming capability, though then of course you have to keep the phone close enough to the stereo to not break the connection.
