I just replaced my speakers last weekend with some Alpines from Best Buy and I hate them. It may be me but I swear they have less base then the original paper cone speakers. The good news is that the swap took less than 20 min and I found a great video on youtube that shows how to adjust the current bracket to accept any 4". I have attached the link to the youtube video below.
http://www.youtube.com/watch?v=W0LPyCoq5k8