I'll jump in as well.
I'm surprised that the OP is building a PC and adding two (2!) devices to make the whole thing work. As has been stated a $99, AppleTV does the trick. Add AirFoil if you want to send packets from non-iTunes sources. If you ever want to expand it, simply adding a Airport Express allows you to send music to a different destination. Just 8 years ago I paid a crazy amount of money to have this infrastructure built into a home I was building. Now, it's all wireless and extremely scalable.
I'm still not clear on why RastaSean is taking pot shots at "overpriced streaming stuff". As has been pointed out, you can stick with your own content, and stream nothing, price-be-damned.
Last summer I streamed some live concerts to the AppleTV, and yes, it was free.