I've heard of many people experience voltage mismatch problems when using pro amps to power their subs and connecting them to the sub out on their receiver. Unfortunately I've had the same bad experience with my previous receiver, the Harman Kardon AVR-510. B/C of the voltage mismatch, output drops significantly and requires the use of an external boost device. Using a buttkicker II and a crest pro amp, I connected the amp to my receiver's sub out only to first discover this problem... the problem precisely being that the sub signal drops. It required a sub setting of +10 (highest setting possible) and insane volume levels to get decent feedback from the buttkicker. I thought it may have been the amp, so I tried using two other brand amps (Samson and QSC), and experienced the same problems. Upon adding an SVS sub to my setup, I would encounter yet the same headache. I had previously used a Midiland sub in my setup that I ripped off my COMPUTER SPEAKERS (S2 4100), and quite honestly it outperforms the SVS, even when the SVS is driven at insane volume levels with the +10 sub setting! That gives you an idea of how bad this voltage mismatch problem is. Some have used the $50 Radio Shack SA-155 to boost the signal to the amp, but quite honestly it's quite a crude, cheaply constructly device that undoubtly degrades the signal. I've gone down the same route only to return the device a few days later. I've become and sick and tired of dealing with these problems so I finally decided to get a new receiver... one that doesn't exhibit these problems. As much as I LOVED the harman kardon (it really was a wonderful receiver), and in fact I even wanted to give the AVR-520 a try just in case it somehow miraculously doesn't have the problem, I really have to move on. So my question is, who here has experienced the same problem with their receiver? Please list the brand and model. Hopefully such a list may be useful for many others as well!