What does a uncentered speaker sound like if you refoam and don't get the cone centered.

It will throw off the proper pistonic motion, which is never really perfect to begin with. In other words, the sound wave propagation will be distorted.

Try pressing with thumb and middle finger using both hands,basically four corners of a square on the cone ..equal pressure on the four points ...down with light pressure moving cone in and allow it to move back...do that a few times and if you feel rubbing its messed....the rubbing will sound like distortion  when audio is run through it....if you redo it again use shims so coil is centered.

I can not get the center dust cover off.. I tried a very sharp razor knife and its not cutting it. I can just cut it off but I wanted to reuse it. Too scared of cutting the cone.