Another Zu Druid user chiming in here. The Eastern Electric M520 drives them flawlessly, better than any other amp I’ve tried; I’ve had a Triode Corporation A300 SE, an F3 Clone, a Cayin A50T, and an HH Scott LK-72 pass through the system. All of these are great amps but the M520 really makes the Druids sing. It’s a first class amp, especially if you have relatively high efficiency speakers. The adjustable feedback feature at this price point is amazing. I don’t think people overstate the case when they say that this is 6 different amps in one. With the flip of a few switches, I can approximate the sound of the Cayin, the Triode Corp, and the Scott amp. In Pentode mode, with no feedback and using the 8 ohm taps, the handshake the M520 makes with the Druids performs competitively against any megabuck system that I’ve ever heard. And with 18-20 wpc, they will drive reasonably sensitive speakers to satisfactory levels in most rooms. I can’t speak for 4 ohm loads but with my 16 ohm loads being driven by the 8 ohm taps, my dial never leaves 25% and 25% gets me approaching concert levels, clean and smiling. The only conceivable knock on the M520 is that it’s not dead quiet. The only tube amp I’ve had that was dead quiet was the Cayin but for me, that’s not the end all, be all. If it was, I’d still have the Cayin.