[Cloudsurfer]

You won't really be able to just replace the dash speakers, rather you'll need a set of component speakers. Your door speakers are currently 5 1/4's, though you can easily install 6 1/2's into the doors which is highly recommended. After that, you need to decide if you want a 2-way (mid-bass and tweeter) or 3-way (mid-bass, midrange, and tweeter) system- most go for a 2-way and put the tweeter up in the dash.

The easiest way to do this is to install the crossovers (which separate which frequency range goes to which speakers) in the front trunk, and then re-use the factory wiring.

Note that to do this, you will have to replace the factory amp (which is pathetic anyway), which depending upon what year your car is, can be either very simple or less simple. If you've gone this far, I would also replace the factory head unit with something newer, which will have far more capability that just playing CDs or the radio and sound better. That said, you can pick up a decent head unit, 2 channel amp, and 6 1/2" components for well under a grand, and have about a 1000% improvement in sound quality and user friendliness in your car.

Unfortunately, when you start getting into upgrading audio on most newer cars, it often becomes an "all or nothing" type project as the factory systems are all designed from the ground up and are proprietary to the specific car they are installed into.

Hope that helps.