more power

I have three 4ohm dvc 12" woofers 700watts each. One 600watt 2ohm amp.speakers are wired in series(Mono bridged). my question is how can I get more power or deeper crisp clean bass. There is little or no distortion now but I see room for improvement. I don't know much about car audio so please break it down. I don't have much money so my options are limited. I thank you for your time and suggestions, all suggestions greatly appreciated.

Hey demond96 , what type of enclosure do you have for these 3 subs ? The type of enclosure will have a direct impact on the sound of the bass you are producing. If you want more bass, what you can do is TRY running the subs in parallel and porting it  or if you want cleaner bass, try to set all your crossover and EQ points to accomodate the car and the enclosure and make a sealed enclosure.

Thanks Jeff. I now have all three subs parellel and the sound is much more deeper. I still have to shop around for a ported enclosure for three subs that won't hurt my pockets. One last question, is there any other way without changing or modifying my enclosure that  will clean up the bass more.  Again thanks for help.