Gerryn,
I am no vinyl expert, but I think going with the JC-2 first might yield the best initial "bang" in terms of SQ. You can always add the JC-3 later when your budget allows. Clearly, a number of factors are involved in such a decision. I think a line preamplifier is the foundation and it needs to be laid first...then you'll be better able to hear the differences between one phono preamp and another. The GCPH is a fine phono, but I suspect you'll better appreciate the JC-3 when it's run with the JC-2. Others with direct experience will obviously know best.