Your receiver has a Toslink port, so the guy in the store was onto something. What you can do is stream from your iMac to your receiver.
What I did was pickup and Airport Express (Refurb about $70). The mini port is both RCA and mini Toslink.
So I bought the cable below, and hooked it into my Yamaha Integrated Amp. I downloaded the free App called Remote.
Now I just open my iMac, set it on a table, and control everything with Remote. The Toslink cable can stream lossless so HDTracks sound amazing.
Not sure if this was what you were looking to do, but works well for me. About $120 all in.
http://www.amazon.com/gp/product/B006XC55ZY?keywords=mini to toslink&qid=1456678814&ref_=sr_1_1&refinements=p_89:Audioquest&sr=8-1