Find online dealers that carry both Garrett and Minelab, try to get a contact name, and start sending emails to those dealers NOW. If you need a few dealer names to write to, just let me know. Tell them you want to buy the ATX & CTX together and what is the best price they will give you on the set. You can start with a email to Bart at Big Boys Hobbies (bigboyshobbies.net).
You should be able to negotiate the ATX down from $2120.75, to $2000.00, and the CTX down from $2499.00, to around $2350.00 or more off.
Once they give you a price that sounds good to you, ask them what they can throw in to sweeten the deal.
When you strike a deal with a dealer, you can tell them your plan, where and when to have them shipped, and your detectors could be waiting for you at your location in SoCal when you arrive.
Let us know what kind of deal you put together, so we can see if you are as good with negotiations as you are at finding gold
p.s. If you could find as much gold on a CA Beach, as you find on a NZ Beach, I will eat my ATX, so go for it!!