l7 sounds bad. help please!!

[Kamakazi_pimp]

hey i got a 06 12" dual voice coil 2 ohm L7 hooked up with a kicker zx750.1 amp to my stock radio in my 02 subaru wrx and it dont sound that good. it kina hits but it dont sound like it should it kina sounds unclear and dont hit all that hard. i got it hooked up at best buy n idk if they hooked it up wrong or if having a stock cd player is the cause of this. i was thinkin of getting a aftermarket cd player hoping that it would fix the problem. maybey the crossover or lack of a sub control is the problem im not sure tho. please help me!! cauus i dont wanna get a cd player 4 nothing if it doesnt fix my sound quality or whatever is wrong with it!