Something to chew on:
The compressor is a funny thing, maybe you should just think about doing an OBA (On-board-air), either a good 12v compressor with tank, or even a fancy York. Also CO2 tanks can be had relativly cheap, but as far as an ARB goes an air tank and a cheap 12v compresor is all you need to make it work.
Even if you don't have a front locker, your going to want to air down your tires, you need something to air them up, or at least have something just incase you blow a bead.
Maybe look at just getting the air done. Then later you can decided which locker is best for you. Who knows maybe they will have the E-locker for the D30 by then.