I'm looking to buy a new HU and want something that works well with the iPhone 5. The AppRadio 2 is much more iPhone 5 friendly as it doesn't require as many adapters (only the hdmi - lightning adapter) to make it work 100% with video out and everything. The X2500BT needs a $100 cable from Pioneer, and a VGA-lightning adapter from Apple. THe interface of the AppRadio is more appealing though. THe question I had is about the rca outputs. I am a car audio newb so even though it doesn't have specific sub preamps, it has rear switchable ones. So hypothetically if I only want to plug in a sub, do I need to have the specific sub preamps that the X2500BT has? The X2500 has 3 sets of preamps (front/rear/sub) and the AppRadio 2 has 2 sets (front and rear/sub). If all I want is a sub + amp setup with this head unit will the AppRadio 2's preamps suffice?