FYI, the factory Protege stereo only puts out 10-15 watts RMS. Connecting a 50-100 watt 6x9 speaker to it will actually reduce the sound output of your system.
If you must keep the factory head unit, I recommend purchasing an external amplifier (50-100w per channel RMS) and a set of components to replace the front speakers. Don't worry about amplifying or even using the rear speakers as you don't need them.
You can fit 5x7", 6x8", 5.25", or 6.5" components in the front. The crossovers can be mounted inside the door and the tweeters can be mounted coaxially, or you can cut a small hole in the door to flush mount them. I know it sounds like alot of work but the end result is amazing. You'll never install a set of coaxial speakers in your car again.