I understand that, I'm mostly concerned about the Amperage, not wattage. Wattage will stay the same, voltage will increase, therefore amperage will decrease. Theoretically it should be greater than 2:1 reduction since the PSU's will actually gain efficiency at 240V.
What is your exact question? Maybe I shouldn't have skipped lunch....
Yes, you will halve you amperage going from 120V to 240V. Yes, your PSU units will run a tad more efficiently (like a couple %) running on 240V versus 120V. As I stated, a 4 card R9 280X rig pulls about 1100W from the wall which equates to ~4.5A @ 240V.