Too Much Bass??

No, but it would help. You'll still hear it, it'll just sound a bit muffled, like it's underwater. If it rattles, something's loose. The only way to fix a rattle is tighten it up, or turn up the volume and drown it out- which isn't always effective...
 
Yeah. A ratchet, torx bit (sorry, dont remember what size) and a hammer and block or wood. Just loosen it up a bit, and whack it down a bit so the hatch has to be closed tighter to latch, and tighten it back up. You may also be able to screw out the bumpers at the corners to shim it out, but this may allow air and stuff inside if your hatch gasket is old. Remember also that your latch striker is supposed too have a plastic bushing on it- if it's gone, worn, cracked, etc it will be loose.