12 is a good start.
Do you have an effects loop?
If so, you can plug your guitar into the xt and then into the effects loop. This will bypass the preamp of the JC.
There is also a "What are you connect to" option in the xt.
If you plug your guitar into your pod and the pod into the effects loop return port you will be using the power amp only and the pod will act as your pre-amp. I do this with my Peavey express transtube Sheffield and my Randall R200G2 and it can make the Randall which has a great edgy sound, sound just like my old tube amp if I want it to.