Looking to redo Monsoon

I'd like to redo the stock system in my T/A completely, but need some suggestions as far as what to do. I'm reasonably competent with electronics, so installation would be left up to me. I understand that I need to find what speakers sound good to me, so I am not particularly looking for specific recommendations, just brands that I should sample or avoid.
My main questions are:
What all needs to be replaced (head unit, speakers, amp, wiring)? As far as speakers go, what goes into building an appropriate component system and where in the car (physically) should they be placed?
I plan to buy things over an extended period of time (six months, a year, whatever is financially reasonable). If this would be a bad idea, I will just wait until I can make one large purchase and redo the entire system at once. This would allow me to buy more expensive components at more distant intervals, though. What should I aim to purchase first (i.e. what is more useful earlier as an upgrade and what should I hold off on until I'm almost done)?
Thanks!

