There is no such thing as a fiber optic speaker - they are all analog and powered by a pair of copper wires. All speakers are amplified - it requires power to make sound. Replacing speakers is just a matter of finding some that you like that will fit in the car's openings.
If you have the HK system, then you have a separate amp in the trunk that is connected to the head unit by the MOST fiber optic network. To determine if you have the HK option, look for the "HK" logo on the speaker grilles. Also, if you have an option in your radio's sound settings for "Logic 7" then you have HK. If not, you don't. Either way, speaker replacement is the same.
As for saving money, that will depend on what you buy. Crutchfielld sometimes has good deals.
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