i would have to recommend crutchfield.com. they have everything you need, and they show you what fits your car, and any special equipment you might need like mounting plates or attatchments. there are tons of consumer reviews too, so check those out.
I always had problems finding a good car stereo or audio review website. I came across this one, http://www.carstereomall.com and its seems pretty good.
I know what your probably thinking, "this is an online store", but thats not the case. They do reviews and it seems that they actually don't have a bias toward their advertisers, well because, they don't have any.
Anyways, you guys should check them out ... http://www.carstereomall.com