As tmdlp points out, each source can behave differently. I'd trust the calibration disc for the 980H to start with. Calibrating for the cable box can be a bit tricky - for example, some broadcasts can be simply wrong (as I discovered the first time I calibrated my old 27" Mitsubishi using Video Essentials and switched over to the local news to find the "on location" reporter looked like he'd been on the beach without sunscreen all day). I'd suggest getting the DVD source right first and then looking for some good cable content to see how your cable box is doing at the moment. If you have Discovery HD, see how Sunrise Earth looks. Darker than you are used to may actually be the result of good calibration, as most TV's start out way too bright and are often left that way.