10 inch kicker sub woofer hissing and rattling?

I have a ten inch kicker subwoofer in the back panel of my ford explorer in the trunk. I recently had a mtx sub and box but it was not powerful enough so I put a kicker instead. I originally had the gain of my kicker amp (450-600W not sure) at 7 of 11 and it was rattling hard but on some songs it still drove clear strong bass. So i decided to tune it and change the bass boost down and the gain down. Right now I have the gain at around 2-3 and it sounds like a normal stereo with no subwoofer and you can still hear some hissing on certain songs. Is the problem the mtx box? I don't think its the sub its self because it still drives clear bass with some songs. What can be the issue and what can be done to fix this?

Speakers rattle when they're forced beyond their limit of excursion- that's then the voice coil physically knocks into the magnet. It is desirable to have speakers that can handle more power than the amp produces. If there's a low pass filter on your amp, it should be adjusted to where hiss is eliminated. The sub shouldn't be getting those frequencies.