I would start by simply connecting the left and right channel analog audio outputs of the cable box and dvd player directly into unused inputs of the 7C (not phono-level inputs, of course).
That won't give you surround sound, of course, and the internal dacs in the cable box and dvd player will most likely not be as good as in a quality external dac, but for purposes of watching cable programs and movies the results could very conceivably prove to be satisfactory. And in any event, there would be nothing lost by trying that first.
Best regards,
-- Al