Sound System Questions, 5 quick questions :) Options

[JonCars17]

I have a few sound system questions.

I'm thinking of adding a sound system to my car by the end of May which gives me enough time to save up.

Q1:
What is the point in putting a Sub (8") in both side doors?

Q2:
How much should I roughly look at spending for the system (components in the front, 2 speakers in the back, headunit and a sub 10" with an amp)? I'd like to get one for qaulity and not the extreme bass.

Q3:
What should I look at when choosing a system? the Sensivity aka the dB?

Q4:
How do I calculate how much amp I need

Q5:
What can I do to stop the car from rattling once it is installed?


I'm a n00b when dealing with cars -_-.

[JFrost9]

I think you got a decent set up going there... ive heard some people complain about the Kappas, so id look around a little more on the sub, just to make sure you find what you want. Also i agree with vyet, you definatley want to get another amp to power your front components, and then use the deck to power your rear co-axs. and i think if you have the money, then you should definatley replace the rear speakers. Also pay attention to Ohms. They can differ from the amps. my .02