An ideal amp will double power from 8 ohm to 4 ohm - so we'd expect to see the Marantz put at least 130 watts into 4 ohms, instead it only manages 100 watts. You really think that won't affect its performance with this speaker system? Experience tells me otherwise.A very typical impedance profile, combined with their measured 87dB sensitivity, makes them anything but a difficult load. Again, the Marantz amp has more than enough power to fry these speakers well before it runs out of power.