What Jack said. The Dominator, and Dominator Bass are the same amp with a different speaker. 12" in the Dominator, 15" in the Dominator Bass. There's also the Power Musette mk2, which is again basically the same amp, but fitted with a different (dual cone?) speaker that was supposedly better suited to keys.
I had a PM mk2 - only sold it because, to get that nice valve break-up, it had to be somewhat cranked, which was stupid loud...