I am looking for a good 12 inch sub, around 1k rms ( to be easy on my stock alt, big 3, and yellow top). I was leaning towards the XFL, but decided to keep looking around. Many options have come up, such as the Fi SSD, AB XR, Sxxv2, DD 700 series, and as the title suggests, the LI. My main question is about the Lethal Injection. What are those weird upgrading options on ssa store? Are they worth it?