http://www.zdnet.com/blog/home-theater/netflix-will-add-1080p-51-channel-surroun d-sound-streaming-to-its-online-video-service-later-in-2010/2641 bluray or xbox with ethernet may do it with a hdmi reciever or seperate cables analog out but not sure confirm in the computer section of this forum.
It should say in the owner's manual. If not, having a digital output on your TV is a good sign. However, you may not want to use your TV as an audio source. Many digital cable boxes and satellite boxes carry 5.1 and many computers do as well. You may have to get a card for the computer though.
It may be possible to get 5.1 from the TV to the receiver from the optical out BUT this is usually used for the internal HD tuner that works with a roof antenna. It may pass the audio signal from the streaming option in the TV bit the streaming audio may not be 5.1, only stereo in most cases. Get a bluray player and enjoy the best audio and video available today. The best movie will not be available in HD and 5.1 from a streaming site as the movie producer do not want to cannibalize there cash cow the DVD and bluray sales.