I have reserved, but not yet purchased, a simpler but otherwise similar routing for a circle pacific fare. My routing is as follows:

LAX-HKG on CX
HKG-SYD (just a layover, no stopover) on QF
SYD-CNS (continuation of above flight) on QF
CNS-SYD on QF, stopping there this time
SYD-LAX on QF

This is a J-class (or D, I guess) circle pacific. I booked it through AA--when I called the main phone number, they transferred me to the RTW desk. But once there, the agent made the reservation with no problem. I currently have it reserved, with a record locator assigned. The fare is $4900 (US), plus any additional fees. I'm not sure what the total will be after adding on the fees, but I should be purchasing it in a week or so, so I'll know then. I'm not sure if it's possible to get a better fare booking through Cathay or Qantas (though I'd love to know it if there is!), but that was my experience with it.

Good luck!

ETA: Yes, the trip is based on mileage--I managed to squeeze mine in just under 22,000 miles, which is the lowest value. There are also tickets available for 26,000 or 29,000 miles. I believe the agent will be able to tell you how many miles. There are also sites such as The Great Circle Mapper, which will tell you the approximate miles for a routing.