Not all car audio is created equal. JVO what is boils down to is how much you want to spend, who you know, and what you can get discounted on.

example: local shop guy, you buy all your stuff from him and he marks you off a few hundred for spending a few thousand. Or if you spend a few hundred he knocks of a few tens.

The key here is how much do you want to spend? What are you looking for in your system SQ(sound quality) or SPL (sound pressure level)? What kind of mods you might want to make to you car.

Those three will get you started.

I am still building my system on paper, gotta know before you buy. research research research.