I am currently using an AVIC X930BT and have pretty much decided to replace it with the appradio 2.  I found it a bit odd that the unit makes you choose either-or for the rear pre out.  due to the factory integrated amplifier harness i have to use in my car(prefer to use anyway), I have to use the RCA pre outs with my install.  My current unit has front, rear and subwoofer all dedicated.  since this unit makes me choose rear or sub, can i use RCA splitters on the front pre outs, IE, split the L from the front to be the L for front and rear?

Yes.