If you have the Alpine system, it's not worth it to add expensive components UNLESS you also add a DSP or LOC with input summing and aftermarket amp. With OE Alpine, there is no full-range signal present. In order to obtain a full-range signal to your aftermarket speakers, you'll need a DSP or LOC with input summing (LC6i at minimum). You'll also need a lot of patience. The front door speakers only have low-mid range. The rear door speakers only have mid-high range frequencies -- with treble boosted. Believe me, I tried using the cheap/easy route, and tried many combinations. Nothing made a significant improvement until I added the LC6i. If $ were no object, DSP would be ideal.