Found your answer earlier in this forum topic : HifiBerry Amp+ / Speakers / PS ============= Hi Stefan, the power rating of the speakers is practically useless. It only tells you, what maximum power the speaker can accept without being destroyed. However you will notice this just by listening. Basically you can use ANY 4-8 Ohm rated speaker with the Amp+. This won’t damage the Amp. You should select the speakers not by power rating, but listen to different speakers and choose the pair that sounds best for you. The power output is about 45W peak power into 4 Ohm at 18V. At lower voltages and higher loudspeaker impedances it is less. At 18V, we recommend a power supply of at least 3A (or about 60W). Best regards Daniel =============