[BigFuzzyArchon]

Alright, ive done lots of research and I only got a few questions.

What I want to do is add a new headunit w/ built in crossover in it. Add an amp+sub and keep the factory speakers.

The crossover is so I can turn down the bass in the factory speakers because it pretty much sucks at higher volumes.

I am 99% sure I only need a 2-way crossover for me to accomplish this.

The HU I think I have decided on is the Kenwood Excelon KDC-X790 (here)
which has System E's+ Advanced Crossover system w/ Front/Back HPF and the Sub LPF.
It also has a built-in amp switch which I believe will help since the headunit is going out to amps and it does not need to use its own amp for the speakers. Correct me if I am wrong.

I am not too sure on which harness I should get to integrate the stock amps into my system. I read that I should not get the Scosche adapter and get the Metra harness. Metra's website says I need the Metra 70-5511 harness. Here

Last I am worried about vibrations from the trunk once I put a sub in there. I hear that because I have a convertible and there is barely anything between the trunk and cockpit, that it would be louder. Would this cause more or less vibrations in the trunk? I would be glad to avoid dynomatting my car.

Thanks for the help :thumbsup