I'm partial to Infinity, I had some Kappas in my car. Little 4.5inchers though, just to replace the stock ones I blew the week after I put a mp3 player in it 4 years ago.
For comparing diffrent speakers and such, I use
Crutchfield, but shop around because they tend to be expensive. I did buy my Kappas from them because the only other place I found them was some random really sketchy place online for $5 less.
Also, I don't know if current mp3 playing units do this, but mine would take upwards of 2 minutes to start playing a mp3 disc when I put one in or turned the car off. I bought the second one out on the market, so they probally have gotten better, but I had no idea it would do that. Made the mp3 just about useless for about town, but still great when I did things like drive to Indiana in 7 hrs.
Wetzel