[Phlogiston]

I did this a couple of times, before I found some good paper suspension cones which are much more authentic.


   

Just in case somebody doesn't know what I am talking about - the replacement cone above has a very compliant foam surround.

This makes for a very nice improvement over stock, especially in bass response.

I believe that if you are going to change something, this(!) would be the most effective. You don't need to change anything in the radio, not even the speaker, just the cone.