Does the quality of the line for digital cable have to be better than analog?
Not really. My first step when doing a digital cable install is to see how the TV channels look, and see if there is any ingress. Just FYI, digital cable will look the same no matter how good or bad a signal you get. When you are watching a digital channel, it is almost as if you were downloading a movie from the internet and watching it on your TV. Even if the signal level is really low, if the digital box and recieve it and decode it, it will still look good on your TV. Digital Cable does not generally require that the line be as conditioned as a cable modem line. You still want the signal to be good (between -8 and +12), and you do not want an excess amount of ingress or your digital cable box will not get an IP address. If a cable modem will run on the line with no problems, so will digital cable.
