To connect the sources that are used with the stereo system in the corner to the surround system in another location you could use the record out of the stereo system to connect an audio transmitter. That would send the audio to a wireless audio receiver connected to the surround system. Could be bluetooth or any other type,
Another solution would be to add a Sonos Connect to each system. That would give you two independent zones with great control. The Sonos Connect has an input so you could use that to send audio from one system to the other but you might not have to since Sonos plays so many streaming service, internet radio, and music files. More expensive but much more flexible and expandable.