I thought I would ask about how significant that 0.5 ohm dcr might be. My sansui 5000a has a damping switch on the rear. The two settings give either 50 or 15 for the Df using an 8 ohm load. And all the switch really does is...tada!, add a 0.3 ohm resistor in line with the speaker output. Maybe because the output is via a bigasscap(2200uF), but these specs show that 0.3 ohms added resistance cuts the Df in this instance by 2/3's. Doesn't that represent a reduction in the amps ability to control the motor? Sam