Question about Kicker Sub and Amp?

I have two 15 inch kicker solo baric L7 Subs that are in a big vented box And a kicker Amp that puts out 1300 rms on 2 ohms (Kicker ZX2500.1). Why is it that i am not impressed with the sound quality it is not as loud as i thought it would be and if i put it to high it starts to crackle. WHERE DID I GO WRONG!!!!!!!!!!!!!