If you want to stream to multiple devices, setting up a NAS is probably the best way to go. A NAS (network-attached storage) is typically a small linux box that barely uses power when compared to a full-blown fileserver, but accomplishes more or less the same. You can then stream to all networked devices in your home network (and, with additional configuration, outside your home network).
Example of an entry-level NAS: http://www.synology.com/products/pro...S112j&lang=enu
This is fine for small projects like yours, but you'll probably want to upgrade a couple of years later on.
Now that you have one of those hidden in the laundry room, all you need is a media player that supports streaming over SMB or NFS (or, if you REALLY have to, UPnP), and you're done. I use a Dune HD Max device myself, which is great, but there are cheaper alternatives.
I would highly recommend that you don't
stream wirelessly though. It's slow and will quickly become aggravating. Just imagine watching halfway through a 3 hour movie, just to get a playback error because the playback position caught up with the buffer. In the best case, the player will handle this by showing you a loading screen until there is enough buffered data, but I've seen this crash the playback more often than not.
Fair enough, no 3 hour movies and the problem is solved? Try streaming any content to 2 or 3 devices simultaneously.
In all seriousness though, you'll save more on the ethernet cables than the USB WiFi dongles that you need to buy seperately for most streamers. So don't torture yourself.