I'm thinking about getting a 5CH amp (4 speakers and 1sub) this way the stock sub won't go to waster and also want 2 12" subs if i do this coz of the combination of the stock sub and the 2 12" make it sound horrible ?

 

throw it away the stock bose sub is terrible

 

Stock sub is useless, destroy it.

 

Agreed.. unless you could make it purely midbass, it is useless.
All in all, once you turn up your sound so that your subs sound good.. it will probably blow anyways.