Fuses to protect Subs

I know that there are ways to cut down on distortion from going to your speaker but how do I limit the RMS that goes to the sub.  I have managed to blow the 1 or more in my subs.  I have the MTX 6000's.  Because of limited space these are about the only subs that would work with out me lifting my back seat.  The system is in a 1999 dodge ram quad cab. 

I also know that by keeping your system low you can prevent your speaker from blowing but is not the answer I am looking for.  I am looking for ways to convert watts into voltage so that I can fuse my speaker lines so that when the watts peak out I don't blow my subs. 

So, if I can pick on you, don't mind and no offence either but let's draw a comparison.

If you have a 5.0 Rustang and you do the pilsbury tire bake off, who's fault is it, the sh*tty tires or your heavy foot? Would training wheels or the most expensive tires solve the issue?

If you are blowing a sub it is because you are asking them to do something they are not designed to do, that is play distortion that creates heat or not giving the speakers enough time to dissipate the heat that is generated from continuous play. If you have the bass control on the cd player turned up, turn it down, if you do not have a sub level control in the cd player, get a cd player that has one, double check the crossover point, turn the gain down. These are the common causes of a blown speaker. You want the system to play stinkin loud and safe right? You have to work within the limitations that they are designed to operate in, you are asking them to do a job that they are not designed for.