Why do you need a post-2011 Mac exactly? I have a 2007 MacBook Pro and have been using AirPlay (formerly AirTunes) since 2008 with my Airport Express. I also have an AppleTV which works fine too with AirPlay.
Which brings me to my next point, if you have an existing WiFi network (who doesn't?) you can just buy an AppleTV and connect that via optical to your receiver. The Airport Express may actually make your WiFi network better though.
Final thing: if you have an iOS device you can push music from that or download the Remote app from the App Store. The Remote app lets you control your computer's iTunes library from your phone.