I have an 02 sunfire, 2000 is lots for a system, i spent far less on mine, and it goes pretty good. Best bet on a sunfire in the door is drop the 4x6 and get a decent 51/4 component set, you just need to make some mdf rings to get them to fit, made mine out of 5/8 mdf. disconnect or take out your back speakers they are useless. Box wise you cant go much bigger then 2.5 cubes net, thats what mine is with 45 inches of port area, so 1 12 or 2 10s ported. Get a nice mono amp for the sub, nice 2 channel for the fronts, a decent deck that has 3 preouts and your set.

Phil