Russell745, you could consider joining Ambassador and use the BOGO (if it arrives in time) at one of the ICs. Then you're redeeming points for 6 nights.
I've not stayed at the HI GM before but for 5k points more I would consider IC GS. Had an excellent rewards stay there in Nov. Was upgraded and escorted to my room. IC HKG is nicer and more modern but seems like the staff there are more snobbish and don't really care.