I have this exact question, I have just ordered a Panasonic CT-32HL44 HDTV ready TV with HDMI inputs and I have a Motorola 6200 cable box with DVI outs and I'm looking to buy a DVD player with DVI or HDMI outs on it, but there is only one input on the tv.
I see your point that not all digital cable is shown in HDTV, but NO dvds are hd resolution, they're only what 480 P.
So I guess the question still stands, which to hook up to the HDMI input? the cable box or the dvd player?