The previous owner of my car was pretty hard on mine and they have been needing replacement since I bought the car but now it's getting pretty bad. I'd love not to have to reinvent the wheel and thought I would see what others have done first and had good results with.

 

I put coaxial 3.5" in uppers, 6.75 component woofer in lower ( did not install tweeter or crossover ) . Very pleased , not as load as with a after market amp but load enough to make my wife get mad. The sound quality is much improved, the coaxials get some nice high range out. I can run at max vol without noticable distortion.

Then I got the IA harness and put a 10" 250W bazooka behind my seat, running about 1/2 power and can easily be unplugged and removed if I have 3 passangers.

PS the factory speakers are super cheap paper with very small magnets.

 

Mine came with the factory HI-Fi upgrade, but I changed the front door woofers to the later HK models and it made quite an improvement. There should be some threads on it if you search for it.