Information about the audio system for your car should be supplied by your dealer, ask them. The number of speakers and sizes would be measurable by yourself, as you have a vehicle right there.
If the speakers are altered, and not by Hy or their expensive 3rd party installers, then you would most likely void your warranty on the WHOLE audio system. Given that this system also contains the clock etc AND that some cars have had replacements of these units. I wouldn't be making any changes at all to anything related to the sound system. For most people it's quite an adequate system as is.
I cannot understand why the pursuit of huge sound is necessary on a transport vehicle, surely the place for that is in a nice quiet anechoic chamber. (Preferably underground).