Remember I take it you don't share the coax with anything else but it's not a perfected system. You try it, if it doesn't deliver you give the maker a call and if that fails you return it.
Below is a diagram of my setup. When I plug into the actiontec box upstairs directly I get fast internet (70Mbps)
when I plug into/log on to the airport express upstairs i can only get around 20 Mbps. What am I doing wrong?