[Fraxum]

OP I started out the same as you with the ******** bass harness, amp, and sub (just one for me) and later added the second set of wires (they are already in your harness) and added the other stuff Steve sells (second harness and 6x9 tweeter bypass) and a second 4 channel amp.

Steve's kit worked great and yes, there is some improvement. However the difference is not all that great. Maybe replacing the speakers is needed.

But I am not happy with this setup. I am going to take out both amps and the passenger side amp board and go with a single 5 channel amp.

It will sound about the same, but will save weight. Since you have 2 subs already this would not be a good direction for you.