If you just want it to sound good and you aren't interested in winning any contests or havin the most thump in the parking lot just go with a decent name brand 5-channel amp. Ur sub can take up to 600w? That doesnt mean it needs to get 600w to perform well. Most factory head units only pump out approx 10-15watts rms to the speakers so any 5 channel u get will be sufficient since they mostly all pump out minimum 25watts rms power to 4 channels and more to the sub. Just push 300-400watts to ur sub and ul b good.(rms watts, not max watts) U cud also bridge a reg 2 channel amp to push ur sub if u needed to.
I suggest reading up at crutchfield .com. They have a lot of info.

 

And ya, 4x4 is right. U shudnt decide anything until u know what sub u hav. 2ohm and 3ohm is a big difference.

 

Mine is the 2ohms version. Even though JL put the old instructions in the box that says its a 3 ohm. I was really confused at first.

 

Your amp will do 600w RMS @ 2 ohms. So under power isn't your problem. I would check your amp and loc settings and wiring. Make sure your pre-amp input voltages are set correctly on your amp. Also keep in mind with the wiring is that you have a 5 ch amp and a 2 ch in/3 ch out line output converter. So it would be very easy to wire incorrectly. If you can draw a diagram of how you have it wired we could help even further. One thing to consider as well is do you have base or premium stock system. Cause if you have premium and you tapped the speaker level inputs for your loc after the factory amp than the loc could be sending out a bad signal to your amp since the signal your loc is receiving is already amplified.

 

Thank you everyone for the help! I re-checked all the wiring (unplugged it all and plugged it back in) and it sounds great now. It hits very clean! And has a lot if potential if I wanted to make a lot of noise (not what I was going for) If anyone wants help or info in the upgrade let me know. The stealth box install was kind of a pain because its not really made for past a 2010.

 

And a little more on the system I installed a LC6i for the interiors (not to lose any of the signals/sounds for any channel) and a LC2i (with bass knob) for for the sub channel.