There are a few things you should consider before deciding what 6x9 speakers you need. Firstly, where do you want the speakers mounting, in the front or back of the car, in a built in console? Do you want to display them or hide them? What type of audio do you want to achieve from them (there are more than you think) are the speakers to replace other factory speakers or are they to complement other components? And do you need them amplifying? As you can see from a few sample questions there can be a lot of thought required before purchasing the correct speakers for you.

Hopefully i can provide a little information that will help you make a decision.

First of all and probably the most important, where are you going to mount them. 6x9 speakers are an odd size that very few vehicles cater for. This means you will have do a little more work to install them. Either cutting into a parcel shelf (which i wouldn't recommend, unless you like the untidy look?) or boxing them and building a surround. This is usually done in the boot but is some 6x9 can be added under seat or hidden in consoles. Which in my opinion is the better option as installing them in the boot reduces the sound (which is the reason you want them right?)

What Audio do you want from them?

6x9 speakers are good at producing mid range sounds, this is why many people use them in conjunction with subwoofers and tweeters. Most 6x9 car speakers are capable of producing a decent amount of bass, and can achieve quite high frequencies as well, so there often used to bride a gap between Subs and Tweeters to stop the mid frequencies being drowned out.

Are the Speakers replacing any other car speakers?

Well the chances are that your car will not have 6x9 speakers, but this does not mean you can't install them. Often a amplifier is needed to power them, however you can wire straight from the speaker out sockets on the stereo. If you wire from the stereo it's likely that the 6x9 speakers will be under powered, and the performance of the speakers will be compromised.

How much do I need to spend on them?