If you decide to go with Two I HIGHLY suggest a thermostat. Big Apple makes a good one (see the BAH-1000) Even if you only use one and a light or something it really does make life easier. Just a suggestion
Bob lives in the basement so I have to use 2 heating pads. On his cool side I use a under tank reptile sticky pad and it stays between 78-81. On his hot side I use a human heating pad and it runs 89-91. If I did not have one on his cool side it would drop to 68-70 which is too chilly.