This will be a slow work in progress, as I work in a 100% commission job.
First thing going in will be the Clarion VX400.
A double-DIN touchscreen is a must for me, as is iPhone integration. This one has built-in Bluetooth, which is another feature I really need for mobile calls. I can add on the navi if I want it, but the iPhone is more than adequate in that regard. Can also add on HD, SiriusXM, and a rear camera for reasonably cheap. And the price is pretty damn good at $365 shipped. Of course I will need to get the navi bezel as well...
I've never had a vehicle with dash speakers before, so this is new to me. I've always done components up front with tweeters mounted to the sail panel. After checking out Matt's threads extensively, I will most likely do something similar, with a full-range in the dash and a beefy mid driver in the door. Maybe just a 2-way in the rear doors.
As far as a sub goes, I won't be able to give up much cargo space, so something like a Stealthbox may be my only shot. I don't have nearly enough time or expertise to build/fiberglass something like that myself, so I may just have to pony up the dough.
So the plan right now is headunit, then speakers, then an amp. By the time I'm ready to add the amp, I should know what I'm doing sub-wise, so I'll know whether to go with a 4- or 5-channel.