Re-Read the Last Line of my last post.
The rear drums have to working properly and properly adjusted for the front brakes to work well.
The front disc pads always ride on the rotor, they are self-adjusting by nature, as they wear, they just move closer to the rotor as they ride on the rotor.
The rear drums, the shoes wedge themselves into the drum (thats why they take realatively less force to activate the drums, than discs), the shoes have to pulled back from the drum by springs. So as the drum and shoes wear, the distance between them increases. You have to adjust the rear drums to remove that slack that comes from the wear.
When you stomp on the brake, the master cylinder creates pressure to push the slave cylinders out and activate the brakes. None of the brakes activate until the pressure is built up in all the brakes. So any slack in one brake, will be felt in all the brakes. So, if there is lots of space between the drum and shoes in the rear brakes, your pushing in the brake pedal doesn't do anything until the rear shoes extend enough to actually contact the rear drums, then pressure starts to build on all the brakes, but by this time you've got the brake pedal pushed half way to the floor and it will get to the floor before you've built enough pressure to give you a really hard stop.
Adjust the rear drums, that will remove the slack in the brakes, you will get more of a bite from the brakes much sooner as you press the pedal down. That give you more pedal to push even farther and get even more braking force.
Your rear drums should have "SELF-ADJUSTERS". They are designed to "MAINTAIN" the adjustment of the rear drums. If your rear drums are in good shape, working properly and are close to proper adjustment, the "SELF-ADJUSTERS" will help keep them that way. Usually you just have to slam on the brakes with the car moving in reverse to activate them, and it will adjust the rear drums. You may need to do it several times if they are more out of adjustment.
BUT, THE REAR DRUMS HAVE TO WORKING PROPERLY, IN GOOD SHAPE AND CLOSE TO PROPER ADJUSTMENT. The vehicle is 15 years old, and judging from the brake performance you describe, the previous owner never did that. I'd pull the rear drums, inspect them, clean them, correct any problems and then lube them up. Then adjust them manually. There are lots of little linkages, springs and sliding parts, that rust, sieze up, drag, etc that mess up the rear drums. The front brakes often suffer until the rear drums are working right. You should see much better brake performance after you get the rear drums working right and adjusted properly.