Sub problems, please help!
 

So I just brought my car back from the mainland to hawaii, and i guess somehow during transit my amp went missing.... >.>
anyway, I got a new Power Acoustik 2600 watt amp and ive been trying to install it for the past couple of days. I have an aftermarket sony double din wit sub output and i ran my rca cables from there, power ground and remote are clean, amp is getting twelve volts (checked with multi meter). However, when the amp is low, no sound comes out of the sub watsoever, and if i turn it up to almost max, its a really low amount of sound, i can see the sub vibrating, but if i get in my car, there is no noticeable bass at all. Ive installed sounds before in many cars and ive never had this problem so if anyone can help me out, i would really appreciate it.
Thanks in advance :D

P.S. 1 12' Kicker comp in truck box since thats all that fits in the trunk.... dont kno if that helps

Double posting.