I am not familiar with the Elura, but I can tell you in order to take advantage of the HD capabilities of your TV then you will need HD equipment as well. Many people learn this lesson when hooking up regular cable to their HDTV. They assume the quality will be in HD since its an HDTV, but that is a wrong assumption. When I hooked up my standard cable into my HDTV the quality was actually worse than it was on my old box TV. For cable television, you will need an HD receiver with an HD signal in order to get HD quality in your HDTV. So again, I am not familiar with the Elura, but based on how HDTV works, I would assume this is the case.
If the signal that the HDTV receives is not in HD format, then the picture displayed on the HDTV will not be in HD; the source must be in HD as well.