The 4-Channel is a good way to go, I went that route myself except I used channel 1 & 2 for the 5 1/2" infinity components that I installed in the front doors and I bridged channel 3 & 4 for the 10" sub in the back. I mainly listen to rock and I am very pleased with this setup.
It was a power acoustik amp that put 70w rms to each of the channels and 180w rms bridged to the sub. I didn't power the dash or rear speakers but if you want you could do what I did then install some new dash and rear speakers and power them with the head unit. Here is a pic of the sub box I used (which I'm selling btw to help raise $ for dsmlink):