First of all, thank you Sebastian for realizing this absolutely useful idea.
Unfortunately, SWYH does not list my DLNA enabled Harman Kardon Aura. It is already connected to my wi-fi network, listed as a Media Renderer/Device under Win-7 and I can play it via Spotify Desktop/Connect.
Is it possible to make SWYH detect it, e.g. by manual setup from the command line? Any help will be greatly appreciated.