If you just need another set of outputs you could use a high quality RCA "Y" cord.
You could ask on the CJ owners forum to be sure but it looks like the preamp has a cathode follower output stage and a 2uf coupling cap so it should have no problem driving the sub amp as well as the main amp.
You could ask on the CJ owners forum to be sure but it looks like the preamp has a cathode follower output stage and a 2uf coupling cap so it should have no problem driving the sub amp as well as the main amp.