Frank, make sure you are getting M300s that have had the PS upgrade. I believe the retail price of those amps is actually up around $16,500 for a pair that has had the upgrade. If someone is telling you $13,500, those may not be upgraded amps. I recommend contacting Wilson to confirm the amps have been upgraded, based on their Serial numbers..
On another topic, I believe the CJ LP140s are supposed to be sonically different from your Model 12s. Another reason to listen to them before buying, if possible. Maybe LP140 owners could weigh in.
Finally, if there is no deadline on your decision, I recommend trying a free audition of the Ncore amps in your system. You might be surprised.