i have a 2015 GS with an aftermarket sub. Thinking about adding an LC2i to help offset the bass roll off the factory amp does. Will this work or does the factory amp roll off bass to the mid-ranges too? Will I have to add an additional amp for the other speakers too?

 

The LC2 will only correct signal for the amp you have it hooked up to. If you're trying to correct the roll off to any other speakers, you'll need a processor with more outputs and more amplifiers. Take a look at the JL Audio fix86. We use that processor a lot in factory integrated systems and have had really good results with it. It will correct and clean up any signal issues the factory system creates! Then feed that signal into aftermarket amplifiers. The fix86 will give you 6 channels of output but if you just want something for the sub only, you can use the fix82 which is just a 2 channel version. I'd say do the fix86 in case you want to add more amps later. Another nice thing about the fix processors is that they are super easy to setup. It basically calibrates and adjusts itself.