Being a confirmed fan of Class A (Sumo, NEW, Classe, Atma-Sphere, Llano and now Plinius) and planar speakers (ML, Soundlab and now Apogees), power is a major issue in my audio life. I don't believe you can have too much. Having said that, there are volume control, sound quality and heat issues as pointed out above quite accurately (Fatparrot - Plinius amps have a bias switch that allows you to keep the amp warm in AB and ramp up to A in a few minutes - a very handy and unique feature, even better than the standby mode of tube amps). Could I cook my ribbons if I cranked the Plinius all the way up? Probably yes. But I couldn't stand to be in the room, so I think I'm safe from power excess. At the same time I've heard JA-200s clip on acoustic guitar through Apogees - 180W of Class A tube power was not enough! I would compare power to breast size (or horsepower if you like the auto analogy): in general, more is better, but after a point it becomes ridiculous! Let your results in your system be your guide.