I would use the 150,000 for a RT in QF Fto Australia (135,000 miles). I booked my flight 330 days in advance and got the flights I wanted all the way on QF metal (JFK-LAX-MEL-SYD-LAX-JFK). From MIA you would probalby fly CO to LAX, then QF. Just plan 330 days early. I have looked at the availability 330 days out for next year and its there. You just really need to book early. You can redeposit the miles if you change your mind, albeit at a fee as a silver.
IMHO, this is the best use of CO miles.