My 19V 6A power supply is a laptop-style brick, I think HP branded; I don't remember where I got it. I wonder if replacement power supplies for gaming laptops might be a good match, as the graphics cards for those laptops would have pretty big power requirements. I see Amazon has a few 19V 9A supplies, which may be overkill. I'd like to find something around 30V 6A, as suggested by @Yatsushiro. True, I would never use that much power, but I'm curious about whether the amp would sound different with extra power in reserve.