What to update first: pre or power amp?

So, I am seeking all opinions on this (if you read the Asylum you will see the same thread). I am looking to upgrade the sound of my MartinLogan Aeons by going from Rogue Magnum (66 and 88) to the CJ Premier 17/140 combo. However, I am not sure I can do both at once, and my only local CJ dealer doesn't stock the 140. What do you think would make more of a difference in the system: upgrading the pre from the 66 to the 17LSII, or upgrading the power amp from the 88 to the 140?