I think a lot has to do with how demanding your speakers are; can they use the extra power?
I read the Stereophile review of the JC1+, what struck me the most was the price jump of the new amps vs. the old.
BTW: in the 2003 review of your JC1 by Michael Fremer he states that the amp runs in class A ’up to 25 watts’ so no change there.