Thank you for the reply. I spoke with Customer Service and was informed that Digicard can receive additional channels but no video on demand, which would include Replay. This is too much of a downgrade, so not of interest.
For general information, I have the Connect & Play 500 package with Horizon box. A Digicard is available at additional monthly charge, or I can return the Horizon box and build a (new) subscription based around the Digicard instead. Since it does not meet my technical requirements I did not pursue the question but I mention in case of interest to others.