1947RBT,
You would need more than 2X amps from 6 to 12 inversion unless you have 100% efficiency, however, items running off 12 volts only require 1/2 the current for the same wattage, so you're only out the efficiency loss.
The only reason I can see to have a split system is if one wanted to have an original look, but hidden 12 volt devices.
