Yes you can use more then one cabinet as long as the total load stays around 3-4 ohms. Anything less, and you may overheat the power amp. I believe that your amp has 2 speaker jacks on the back.
As for the "Module" output, this is a low level signal and not a speaker output. It is for driving the input of a power amp. Back in the 70's Kustom made speaker cabinets with built in power amps that could be added to your system to increase the total power/watts of output. This way you could control 2, 3 or 10, 100watt amps from one control panel (head).