Drudis

Greetings from Lexington,
I'm very new to the site, and I have some pretty basic questions. I'm looking to install some cheap audio equipment (Kenwood KAC9105d and 2 Audiobahn AW1200q's single chamber ported @38hz) in my TL.

1. I have an 04 TL with Navi, what are some of your opinions on using 4AWG wires and 900w RMS with the factory alternator? I know that if it's too loud the lights will dim either way, but I really just need to know how many Amps the alternator puts out and how many people on here have installed aftermarket alternators?
2. Using speaker level inputs, what is the recommended input sensitivity (where do any of you with speaker level inputs usually set the gain?) And I'm assuming the rear 2 speakers (wires) should be used for the speaker level inputs?
3. How difficult is it to find a way thru the firewall? I haven't decided if I'm going to install myself or not, any suggestions?
4. How long of a power wire will I need? Will 16ft be enough?
All advice is greatly appreciated. I really wanted to get crazy with the system, but I'm hesitant because my 12" Infinity Perfects, JL 500/1, and Kenwood Excelon HU were all stolen out of my Firebird. Sons of B**ches even stole all of my pennies and chapstick (seriously).