After a bit of digging through search results, I think I have a good grasp on my newly acquired 100S's outputs. The two jacks are labeled - the left says 8 ohms and there is a bracket pointing to both of them that says 4 ohms. If I understand correctly, one 8 ohm cab = left jack, two 8 ohm cabs = both jacks and one 4 ohm cab = right jack.
I just wanted to check before I plug in a 4 ohm cab...
Thanks!