Just to share. Recently I had purchased system 4 inverter aircon from Gain City. gone thru the process and had my fair share of headache. in the end my hb and I settled for the aircon with 9000 BTU for bedrooms and 18000 BTU for living room.
Initially we intend to get system 3 + 1 type but as our flat does not have the aircon latch so we had to consider other option. My block does not have the higher electrical loading, in the end our selection of aircon is quite limited. You can check with your contractor.