Unfortunately, the correct answer is: it depends. It depends on the specific player and the specific display. Most claim that HDMI makes more of a difference for fixed pixel displays (plasma, LCD, and DLP) than for CRTs like you have. In addition, it depends on which has the better deinterlacer/scaler, your player or your display. The only way to know whether you will see a significant difference with your equipment is to try out an upscaling player and compare for yourself. The only thing for sure is that the salesman who told you that upscaling over HDMI is as good as true HD is wrong! The PQ of current DVDs is limited by the 480i resolution of the actual DVD - no upscaling player will look as good as a true HD broadcast. But with my high end upscaling player (Denon 3910) and my DLP, yes, HDMI does make a difference.