I bought a pair of infinity reference 6020cs (2 ohms) component to replace a pair of polk that went bad. I have it connected to an MTX thunder 404 and as soon as I connect it I get that whine noise. It's fine connected by itself but when I connect both channels I get the noise. The rear speakers are Infinity Kappa 4ohms. Can the problem be the difference in inpedance in channel A and B? The AMP is 2 ohms stable but I'm not sure if both channels need to see the same load. Thanks