Hi Andy,
You could have the concert pack installed.
Check if there are grey speaker rings on the rear doors with "bassworks" on them.
Not sure how else you can be sure without taking the car apart.
It
could have aftermarket speakers fitted...
The head unit is the standard head unit as in all EXs.
The firmware version will not tell you what speakers are installed.
Lots more info in the Wiki.
Radio Firmware - How to find version - Civinfo Wiki
In Car Entertainment - Civinfo Wiki