I installed a new JL audio powered subwoofer and removed the OEM altogether. You can't just replace the existing sub, as the stock amp isn't pushing much power to the sub channel. I also wanted to keep my trunk space! Here's my process:
1. JL Audio ACS110LG-TW1 gave impressive sound in a box that was only a foot tall, 1 1/2 feet wide, and 6" deep. I feel that I still have the trunk space to carry whatever I want.
2. We bypassed the stock amp completely and wired directly to the head unit. Added a bass control knob under the steering
wheel, as I listen to all types of music and need to tame the bass beast at times (or release it). Added dynamat sound deadening to prevent any rattles. This was placed on the rear speaker deck where the factory sub is located.
3. My installer originally priced and installed the 10", but upgraded me at no charge to the 12" version, because he didn't think there was enough power to push through Genny's sealed-up trunk.
4. The 12" version thumped and damn near tore the rear view mirror off the car! Thought about toning it down and only occasionally gluing the mirror back on, but one wrong move and I might liquefy the insides of my back seat passengers...asked to hear the 10" sub.
5. Took 5 minutes to change out, so I recommend trying out a couple of boxes/sub sizes to get your preference.
6. The 10" was much better suited for the car and for my tastes. I can't stress enough how adding the bass and mid-bass really smoothed out the overall sound... subduing the mid-range and even slightly enhancing the highs. I was not expecting that. I know I'm not crazy, because I was only out of the car for 3 hours...I knew what I had going in, and what I had driving out with a big-ass smile on my face.
Hope this helps!