It is solid state, so it depends on the cabinet. It is something like 350 into 2 ohms, if it uses the same power stage as a 320 head of about the same age. It also depends on how much clipping you are willing to live with. It will put out more power with clipping than clean power, like every other amp, but the ratings are all over the map, so ratings are in the eye of the beholder. I have found that to be more than enough out of my 320. The old 360 stack is rated at something like 200 watts, and it keeps up just fine. I don't really know why. Changing standards perhaps?
Cranky old man. Cranky old bass. Cranky old amp.