The '43' antenna in Australia is special in that is has an optional 400kW S-band high power amplifier, instead of the usual 20kW. A note from the manual (70-m Subnet Telecommunications Interfaces) states:
400kW Power Amplifier
2110 to 2118 MHz Only available at DSS-43. Cannot be used above 100 kW without special airspace coordination. No operation below 17 degrees elevation is allowed, no matter what the power is.
It is uncommon to see general HPA efficiencies above around 40% so they are looking at around 1MW of AC input power just for that amplifier when in use. The smaller 34m dish could be used, in theory, but they would need about 1.6MW of RF power, so around 4MW input AC to run it. And of course the RF route would have to survive 1.6MW without anything flashing over!