There are 2 seperate components:
One is the media player such as Asus O!Play and Western Digital TV Live, which can play (output) all the various media files to your monitor (HDTV or whatever). I've had an Asus O!Play for a few years and it's pretty good.
Then you also need storage. The media player can be used with a wireless network if you have that at home so you can play files from your PC. Or you can get an external HDD in a case, and store the media files on that, and connect that to the media player either directly or through your PC.
Hope that helps. And don't go to Future Shop or Best Buy - try
www.ncix.com, great prices and they can help you figure out what will best suit you.