IMO the new Sony Xplod series car speakers sound so good they might take you by surprise.. now before you flame me..
I used to work with a guy who did custom car stereo and lowriders as a big hobbie.. he's been doing it for almost a decade.. I asked him about which speakers he would prefer and this is the response I got from him and the other people he worked with in his shop..
1. Only get 15 inch speakers if you have the space for some 8",10" or 12" speakers also.. 15 inch speakers move are but the recover so slow that their response sucks so you need a set of smaller speakers to make up for the lost response.
2. Most expensive doesn't always mean they sound the best.
3. Making sure that your speakers meet their air space requirments means EVERYTHING.. you can have $500 speaker but if the box is not made to spec then it will never sound they was it was meant to.
He's also the one who told me to check out Sony's Xplod series.. I got a set of 6x9 three way speakers for around $100 and put them in the back dash of my Caddy and just hooked up to my CD Player sounded like 10 inch subs with semi decent tweeters. Ever since I've put Xplod in all my cars (with the exception of the Kenwood 4x10s and tweets cause Sony don't make them
) because (like Intel vs. AMD) the Xplods are the best bang for the buck. I've heard that their subwoofers will really surprise you but haven't had a chance to buy them yet. (Got a really good deal on a set of two JBL 12" GT1200 for $50 in a box and I plan on using them.)