Replacing tweeters?

I have an 02 GT conv .with the Mach 460 system. I changed the headunit to a Sony 7715 and put a 10" bazooka in the trunk. Sounds alot better than stock and has more punch than it did. The car is missing some highs though. The headunit is running the 2.5" up front so would it be possible to replace them with tweeters to help round out the sound? Also could I replace the 2.5" in the rear with a set of tweeters also? Has anyone else done this?