Different Infinity models, and even a different Kicker model than I went with, but highly agree with GXP25 above. The Infinity speakers I found were still true 2ohms, and I actually did Kicker DVC 4ohm subs for the back and just wired them in parallel so they are down to 2ohm. The only thing I will say about the rear doors is that I had to trim the hell out of the foam baffles to get everything to slip in to the doors. And I had to just screw them down into the doors without the factory plastic piece, without the plastic piece Infinity gives you, and yeah, I had to just screw into the sheet metal but it's very easy to do.
The baffles are an absolute must for this car. Protection from water is obviously the main reason, but I also installed everything without baffles and then with baffles to hear the difference. There absolutely is a sound difference as well.
The only thing I add to GXP's list above is to also get the 8" baffles for the subs and something for a little sound deadening on the rear deck. The baffles for the subs definitely helped, but also make for a much cleaner look in the trunk as well.