There are hordes of combinations that could suffice for this purpose.

My most recent setup is an older Airport Express Base Station connected to my older Onkyo AV receiver via digital optical in. I stream from various devices over the network using a combination of Airfoil (software) & VLC (media player). Most of the computers involved are running either Vista or W7, and there are a couple of iPod Touches in the mix too.

I also use a WDTV live which connects to another AV receiver via HDMI. An external HDD & various large USB flash drives are connected to the WDTV and contain the media.