i currently have 2 12" cerwin vega vmax powered by a fosgate 700s 2 channel amp. each sub is getting 350 rms. i am getting bored with this and want to add 2 more subs. i know that when u double the power u gain 3 db and i know when u double surface area u get 3db. i cant get a bigger amp because i dont want a new alternator. if i add 2 subs with the same amp giving each 175 would i be louder or the same.