Have you thought about contacting Parasound with your concerns? I've found their customer service to be top notch and Richard responds quickly.
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I've done that and he does. He's been very helpful with JC1, 2, and 3 as well as A23. It may not matter, if I set all three amps to low bias, but if I want to use high bias all around, I need to send the amps in for service. I don't think I want the amps to get that hot, so if they switch from class A to A/B at 10 watts, that's probably OK for 90 dB sensitivity and moderate listening levels.
I found my JC-1s sounded best in high bias so I've used that for critical listening and low bias for background music. Even when I owned Duntech Princess speakers with very complex (read - not an easy load) crossovers they would get quite warm but never what I'd call hot. I could leave my hand on a heatsink without discomfort.
The impedance of the speakers is different, therefore load is different. Replace center JC-1 with one of the others and run your system. If the new center amp runs hot, then it is the speaker load making the difference. If it is not hot like the original center amp, then you would investigate the difference between the amps.
The amps were bought used, the pair that tuns cool from one party and the third that runs hot from another. Given that I think they sound so good running on low bias, I plan to use them that way for the time being. At some point I may send them to Parasound for service, but I'm really don't want three amps running as hot as the third amp does when the bias is set to high.
Each of the amps driving the KEF 107/2s uses two Clear Day cables for biwiring; a second Clear Day cable is on its way for the amp driving the R600C so it can be biwired as well. I suspect that's irrelevant to the issue.