Speaker Upgrade-Changing parts for Neophites?

Is there an easy way to upgrade a mass market speaker. For instance I understand that vifa or seas makes great tweeters. Could I simply rplace the tweeter in my paradigms to improve the quality of the sound? Could I upgrade the caps-How to go about improving an existing speaker? What's the easiest way to improve the sound in an existing speaker?
It is difficult to swap parts and be certain that the result will be a better sounding speaker.
To just toss in a better speaker part, hoping for an improvement... is a mistake.
You might think about looking at some of the kits available from speaker kit makers... like Madisound
The more specific the info that you present us with, the more specific we can be on recommendations. Sean