I think you have calculated incorrectly if each speaker is 70w power usage at its max power ( it should be rate max power) then the amps consumed would be (70w=115v X amps) so 115/70= 1.64 amps, note your speakers require 115v AC and draw 70w max each so your amp draw cal should be based off the 115v ac not the 12v dc so each speaker will draw 1.64 amps at 115vac.
you will need min 140w power inverter then add a safety net - power on inrush protection so double or triple that. you could easily run this off a 300w inverter i'd think.
now yes your inverter will draw more current from your battery as its available voltage is 11-14 vdc but the power is the same, well add in the power to run the inverter. So yes your inverter will draw more amps at less voltage from the battery but out put less amps at a higher voltage into the 115vac.
some one check that please
you will need min 140w power inverter then add a safety net - power on inrush protection so double or triple that. you could easily run this off a 300w inverter i'd think.
now yes your inverter will draw more current from your battery as its available voltage is 11-14 vdc but the power is the same, well add in the power to run the inverter. So yes your inverter will draw more amps at less voltage from the battery but out put less amps at a higher voltage into the 115vac.
some one check that please