excuse the newbie question. i'm planning to get a new HD tv and sign up for either HD cable or HD directv. as i understand it, as long as my TV is HDTV ready, the cablebox/dtv tuner will act as my HD receiver. now, if i sign up for HD cable/sat, am i unable to access my local channels (abc, nbc, etc) via HD? do i need one of those rabbit ears and turn off the cable to access the local channels via HD?