The JC1's require over 1000hrs of break in to finally stabilize so don't give up on them, they are truly one of the few amps to drive your speakers. I suspect the JC2 requires the same amount of break in.
Break the amps in first, and then make a more informed decision against your Pass preamp which is excellent also.
Break the amps in first, and then make a more informed decision against your Pass preamp which is excellent also.