Network Media Server with no dedicated PC

I am researching media servers to connect digital music, picture and video files on a Network Attached Storage (NAS) to a TV and stereo. Most of what I have found requires running server sofware on a dedicated PC to stream files to the hardware connected to my stereo & TV. These include systems like:

http://prismiq.com/products/mediaplayer.asp
http://www.dlink.com/products/?sec=1&pid=318

Does anyone know of a system that does not require having a PC constantly on. My NAS is always running. I would rather NOT have to leave a PC on as well?

Thanks.