GefenTV will send your Ethernet over Powerlines or Coax for $200. Plus, it gives you a four port input so that you can run all those web-enabled devices in your home theater. No matter what you have in the walls, GefenTV has a solution for you.
Discuss "GefenTV Ethernet over Power Lines or Coax Cable Extender" here. Read the article.
200Mb Ethernet over powerline has been around for years.
newegg dot com/Product/Product.aspx?Item=N82E16833124095
Ethernet over coax has been around for years too. It is most commonly used in Verizon FIOS installs. Check out the Motorola NIM100.
These may be rebranded products from other vendors.