
Either an application/media player which can use a media renderer as output device or an app which redirects all audio output to such a device. I select the track/playlist I want to listen to, right click select "Play on" (maybe not the exact wording as my Windows is German) and select one of the two devices (e.g.

On Windows, I can use Windows Media Player to play audio on either device without having to touch any remote control. For example I can use my phone to display photos on the TV (e.g. Pro packed full of features remote-friendly interface. For viewing content add your UPnP share as source when choosing media to play. To enable server check option in Setting > Network > UPnP and add content you want shared. However the TV and the receiver also act as UPNP/DLNA media renderer. It can act as UPnP server, player and renderer.

So far this setup works fine and i can browse through my audio on the receiver. I can access audio from both computers using a DLNA-server software on either computer (built in DLNA-server on Windows, PS3Media Server on OSX). I have a TV and an AV-receiver which are DLNA-capable and which are attached to my home network together with a Windows 7 desktop and a MBP running OSX Lion.
