I have owned and operated a Car Audio Shop for over 25 years. I go back to the days of 4 tracks and 8 tracks. My advice is simple. Be careful of who you get your advice from. I read a guide recently on here and it read like an ad from a magazine for certain brands of audio. The writer apparently likes these brands so he naturally "plugs" them. He may or may not have any "real" experience in car audio.

In my experience an educated consumer is my best customer. Your best system will start with you educating yourself on what you are buying. If it is a head unit then figure out what you want it to do first.Cd, mp3, i-pod, satellite or bluetooth are some of the features and or capabilities. Built in eq? Subwoofer outputs? fading or non-fading outputs? 2volt 4volt or 5 volt. If you do not know what you are buying ASK QUESTIONS!!! No question is a "dumb question" and if you ever hear that then you do not do buisness with them. Dealers will always tell you that what they are selling is THE BEST. This may or may not be true. It may be that they are stuck with just a whole bunch of the wrong stuff. Again research is your best friend. Also check the website of the manufacture. Look for Awards for engineering and sound quality. Chrome looks good, but it doesn't mean it sounds good. How long have they been in buisness? Audio company come and go and I have seen my share. One that recently bit the dust and is now Bankrupt is Audiobahn. They did not attend CES this year and have not shown up at any dealer shows and have no new 08 Catalog. Audiobahn owned several other brands such as Alpahsonik, Visonik, Swiss Audio, and Blitz Audio. These brands are also now down the drain as well.

So beware of buying brands that are no longer going to be around for your warranty or replacement as well as repair. Stick with Tried and true and you will not go wrong. Find a good stereo shop that has been around for at least 10 years or more. If the owners look young then find out WHAT THEIR QUALIFICATIONS ARE.  "I learned it on the street" or I have done a bunch of mine and my buddies will just get you in big trouble.  MECP QUALIFIED.  Basic installers certificate at a minimum for the basic installs.  First Class or higher for the big ones. Good shops will teach you about audio. Ones that won't or will not let you watch or tend to blow off your questions then run like hell from. Look for shops where the customers are not all KIDS. (because more than likely kids are running it.)

Also you need to find out if what they are selling they are an AUTHORIZED DEALER to sell!!!!!!

If they are not then you will most likely NOT HAVE A WARRANTY!!! Buy from authorized dealers only. This goes for right here on e-bay as well. Just cause they say it has a warranty does not mean it does unless they are authorized to sell the product.

Last and most important. IT IS YOUR RIDE, CAR, TRUCK, your baby whatever you call it, it is yours and you are going to have to listen to it the most so, be sure it is what YOU WANT not what your friends want or the sales man at the stereo shop thinks you should have.

There are a number of good publications at book stores on "How to buy Car Audio" They are good at explaining what to ask and what to "look for".  They also break down all the technical terms into layman terms.

Well once again, just be careful and ask lots of questions.  You"ll do fine.