Good morning everyone. Though I have played bass for years, I've always used a combo and never an amp head with separate cabinets. I am looking at stacking two cabinets, one 250W and the other 500W, and am having difficulty understanding the needed power calculations. I've been told that a 350-400W amp will be enough to supply both cabinets, but it would appear to my ignorant brain that 750W would be correct. Is that not the way it works? Thank you.