Ake, using an amp with enough power to drive these speakers comfortably at high levels will not only change the sound when you're head-banging, but can positively affect the sound quality at all levels. Normal listening is usually done at only a few watts at most, but that is merely the average level. Music is dynamic by nature, and as Sean describes so well above, there will be momentary demands for power many times that of the average level, and the amp has to be able easily accommodate these without approaching its limits in order to sound unstrained. Also, the higher-power amp will be better able to rigidly control the driver panels, resulting in less unwanted motion that can impair transient response and decay. The improved bass authority you will get from a higher-current amp will be audible at all volume levels. If the amp gives a more 'open' sound as well, that is probably due to the relative lack of compression resulting in less congestion of the soundstage, wherein macro-dynamic events tend to overwhelm micro-dynamic events as a less-powerful amp is stressed by competing demands. However, I've got to add that Maggies are probably not the speakers for you if your #1 priority is listening at rock-concert levels.