I have Kinetic batteries that have been in my Blazer for the last 7 or 8 years and still going strong. I have an AGM starter battery in my Maxima that made a noticable difference with starting and dimming. I also have an XS battery for my work truck which I haven't had a problem with. I think they are always worth it if you're getting anywhere around 1000 watts and have heavy listening habits. Probably not necessary. They are designed for extreme discharge and rapid recharge. Conventional car batteries are not. Even if your not noticing car power loss the battery is taking a slow beating and likely not lasting as long as it should have.