To be honest, you want more of Apple and their Airport Express. If streaming audio is your only concern, you can pick them up used on ebay, craigslist, or even new, they'll only set you back $100. I like to call it the thinking man's Sonus. (or maybe the frugal-man)
Paired with any receiver that will adequately drive your speakers, you should be good to go. Audioengine actually markets a power plug on the back of their powered A5's for this specific purpose.
I've repaired several Airport Express' that suffered from broken internal power supplies, put them into neat enclosures, and slapped them onto the backs of a few ipod docks. Possibly not the level of sound quality you were looking to achieve, but you get the idea.