The head is '500w RMS (1000w peak)' with '4 ohm min. load' and the cabinet '800w 4ohms'. After trolling the numerous threads regarding 'under driving' cabinets, I just want to ask if I'll damage either piece of equipment. So far, it sounds fantastic clean and with my effects. I use Musicman Sterling and an old Peavey Foundation (fretless and it kills!), a green Russian Big Muff, EHX MicroSynth (guitar model modified for bass), and an MXR Bass Octave Deluxe. I keep an eye on the VU meter and and ear out for clipping and haven't been experiencing any.