i have 2 x15inch fi btl on a Lanzar OPTI 6000D, do you guys think im under powering them??? they knock, but i fell like everything i throw at them, they handle with ease, so im thinking of getting a additional Lanzar OPTI 6000D to pound extra hard.... lets me know what you guys suggest?? or should i go with different amps?? Just a thought.