There is a low price and low quality end and a higher price and higher quality end; you get what you pay for.
When I bought my first vehicle from an automobile dealership without knowing whether I was getting a good deal (on my interest rate; not just on the value of the vehicle) - I pursued a job in banking (as a teller to start) to help me begin understanding good and bad financing practices. You can apply this concept in car audio - by expressing your interest in the field to a local shop that is willing to take you seriously. Once you help out as an assistant, you will move up to installing car audio systems by yourself and before you know it - you're a car audio specialist and everyone's asking you how much they can expect to pay for a nice car audio system.
Besides; working at the company that sells the products you want may help in qualifying you for an employee discount. And what better way to learn than to get paid for it? You can't lose!
On the flipside - do a lot of online research about specific models of merchandise you may be looking for.
