How many people?
This is my initial thought. At the moment Aeroplan is running a deal where you get a 35% bonus on points transferred from partners including SPG. US - Australia using Aeroplan (which gives you access to all *A) is 160k/person in J and 210k/person in F for the roundtrip.
You could take 100k SPG ---> 125k Aeroplan (accounting for the SPG 5k for every 20k bonus) and then you'll get a 35% bonus on top of that giving you 168k Aeroplan miles, aka giving you a RT J ticket for 100k SPG miles. Can't think of a better redemption value than that. Note there is a per day SPG ---> Aeroplan transfer limit so you'll want to take that into account. In addition as you probably know you only get the 5k bonus when you transfer 20k, so you'll want to transfer in blocks of 20k otherwise no bonus (which is why I propose using 100k SPG even though you end up a little of the 160k J price).
You'll want to sign up for an Aeroplan account first and poke around to find out what availability looks like and also taxes/fees (Aeroplan passes along taxes and fees on some but not all partners). You'll want to consider *A hubs to start out of in the event that you can't find something from CLT (ORD, JFK, EWR, IAD, IAH) and then you can just buy the CLT - XYZ ticket. Aeroplan will also give you stopovers (up to 2 stopovers).
Note this Aeroplan transfer promotion ends in August so you'll have to take some leap of faith that you'll be able to find a routing that works for Sept/Oct 2018 since you won't be able to book those dates before the Aeroplan transfer promo ends.
The benefit is you should be easily able to get New Zealand as a stopover assuming award availability since you'll be able to use NZ for the trans-tasman flight and have an itinerary that looks something like this:
CLT - ORD - NRT - SYD / SYD - AKL / AKL - BKK - NRT - ORD - CLT on UA / NH / NH / NZ / TG / TG / NH / UA