Wait stop. Before you go spending lots of cash on a BBK, you need to asess the situation. You should not have issues stopping your vehicle. It's a problem. The vehicle has to meet a certain stopping distance per the federal guidelines.
1: is this problem new? Did it used to stop OK and now suddenly your having issues?
2: your description of the problem is hard for me to follow. Do you have to STAND on the pedal to stop?
3: is your brake light on?
4: any strange noises?
5: when did it start? What makes it worse? What makes it better?
6: what year jeep is this? Did you buy it new? Does it have an intact warranty?
If the problem has just recently started, and the vehicle used to have no issues with the brakes, I'd bet you are leaking brake fluid some where.
So if you have a warranty, take it to a dealer (a different one preferably) and tell them about it.
If you don't have a warranty and want to fix it yourself here's the diagnositic proceedure.
1: check brake fluid. If full, then go to next step, if not fill and rediagnose. If problem still exists, go to next step.
2: check pads. If pads are not worn, go to 3. If pads are worn, replace and reevaluate. If problem still exists, go to 3.
3: check calipers for mud or other debris. Remove the calipers, press in the piston(s). A second party presses in the brake, and observe for proper piston articulation. Check all 4 calipers. If the calipers function, go to step 4, if the calipers do not function, replace/repair the caliper and rediagnose. If the problem still exists, go to next step.
5: check for fluid leaks. During all the caliper articulation, there should be no brake fluid leaking. If leaking move to next step, if not leaking skip to 7.
6: leaks can be damage to the lines, or a loose connection. Find the leak. If a line has a hole, replace the line. If the fitting has a leak, tighten. If the leak is present and the fitting is tight, then replace the fitting. After leak has been repaired, rediagnose and go to 7 if needed.
7: if pads are not worn, calipers function, fluid is full, no leaks in lines are noted. The most likely culprit is the master cylinder.