Congrats man. Is this your first system? Sony and Jensen isn't the best companys in the car audio world, but its a start.
Defiantly work on the front speakers first. A good front stage will make you enjoy your sound system 100x more.
Do you have a box yet? Are you planning to build your own?
For the front doors, you could put in a 6.5 component set, but hat might require you to do a few mods, but it is extremely worth it in the end. It all just depends on how much work you want to do.
"Definitely use crutchfield as a research site, but i wouldn't order from them.... too expensive."
Crutchfield is expensive, but you are paying for the customer service that comes along with the product. They honor their 5 year warranty and will even replace an amp that is borderline out of warranty or something that you messed up.