Car Sound System

I have an 06 corolla S and i have an all factory sound system. I want to upgrade to better stuff. Where should i start?>

I want a good sound system really bad, but I know absolutely nothing about them. So my car has the factory sound system. It’s a Mazda 626. I want a good sound system in it, including a nice subwoofer. What exactly do I need to buy? Do I have to get anything else besides a subwoofer? What do you suggest I get?

Okay well i need help finding the right system for my car. I have a 1997 ford explorer with a stock system. I want a system with tons of bass and is super loud. I just don’t know what size speakers to get and what kind of subs and also like what stuff goes best together. So just put down what you think i should get or what stuff is the best.

I recently bought a car that already had a decent sound system in it… Alpine CD Reciever, the front speakers are Pioneer, I’m assuming the rear ones are too. However, theres no subwooffer. Would I be able to add one, what brand, and how would I install it?

About two months ago I bought a very nice sound system for my car
I got:
2 10" Kicker Solo Baric L7 subs
1 Rockford Fosgate Punch P.1000 D mono Amp
4 Infinity Kappa 62.9i 6.5 door speakers

I have the subs in a vented/ported enclosure in the back of my 2008 Honda Element,
The deck I am using is an Alpine CDE 9870

Any ideas on anything I can do to make it sound better?