If you just replaced it then thats not the problem. How long has it been since you changed the oil in in?
The things that make it shift easy the brass blocking rings. They are a cone shaped thing with teeth on the out side and are between gears. Some people call the synchro. But the synchronizer is actually made up of a couple of parts.
First I think we need to figure out the noise and see if it is somthing to worry about. But go ahead and change out the cable. It won't hurt. And if you can tighten it up a little more. You want it to start to grab about 1 to 2 inches off the floor. This ensures the pressure plate opening far enough not to interfere with the disk. When you step on the pedal the pressure plate opens, the disk is then allowed to slide just a little on the input shaft to release from the flywheel. If the disk does not slide it can drag on the flywheel and cause hard shifting.