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?
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The more specific the info that you present us with, the more specific we can be on recommendations. Sean