98 grand prix premium sound?

I have a 1998 Pontiac Grand Prix Gt 2-dr. It has an OEM head unit with tape player,steering wheel controls, and 12 disk cd-changer in the trunk. It has 8 speakers inside, Front(a 5.25/lower door,and 1" tweeter/upper door) also Rear(6"x9"/rear deck, next to a 4"/rear deck) ALL of the application guides I've seen NEVER mention the front tweeter or the rear 4"??? Also,I'm pretty experienced with car audio and I'm almost positive my car has an amplified system but i can't seem to find the amp.(not in the trunk and I've glanced behind the glovebox. I've heard it may be a bose setup, but wouldn't it say bose on the hu or speakers? I could use some specs.PLEASE.

i have seen the pre amp under the passenger seat,back seat and up and behind the radio. Look for them there. Not sure on this one but thats where they like to hide them.Can't be loud then don't have it.

(power acoustik system)

Head unit- TID-896 7" TOUCHSCREEN

ovn1-5500d 09 and another one coming soon

4-12" mofos 12ft3 box to 40hz (wall)

2 batterys, 1 power

The amp is underneath the passenger side dash. The amp runs all the speakers.sparky