ok, so should I just go for one kicker L7 15"? its 1000rms.
Sure, but in order for it to be loud you need to do the following:
1 AGM/Gel Battery in the back
1/0 Wire from alternator to said battery, to frame ground, and from skin to frame
A true 1000w Amp (see Kicker ZX1500.1, Memphis Mojo, SAZ-1500D, Fosgate 1001BD, etc)
A 5cu. ft. net box after displacement, vented, tuned depending on the peak of your car+ the type of music (and it's lowest played hz) you plan on listening to
Knowing whether you have the extra output from your stock alternator to manage an average of 83A draw (and a peak of say 150A draw). If not, you need a high-output alternator.