Logitech Squeezebox used to be the easiest way to facilitate that. Nowadays there's about a million different ways to do it. A computer running a media server like MediaBrowser 3 passing audio to your stereo would mean all you need is the client application on an Apple, Android, Roku, or PC and give you direct access to whatever content (movies, music) you have shared.
Regarding what Krig wants to do - he wants a cheap speaker/receiver combo to connect to his PC as his sound instead of shelling out for shitty "computer" speakers. Lots of people doing that these days.
Don't fuck around with this - any receiver around $100 off craigslist will do, just make sure it accepts spdif (optical) or HDMI as an input to keep your life super simple.