factory amplifier ie extra audio option fitted, how to know???????

HI from Australia

I have recently bought the 2004 Boxster as previously discussed and its a great fun car.
I am replacing the head unit with a DVD/Nav and have the fitting kit etc and needed to know how I would know if the extra audio package has been fitted.
The dealer claims the upgraded audio, so this would mean I use the line out of the double din deck, but is there a way to check to see the amp is fitted to the car as discussed? Any clues on its location appreciated. And if the upgraded audio is fitted, are the speakers quite good?
I have the double din fitting kit and the climate control conversion plate etc so that bits not to hard.
I just want to order an iso plug to suit and of course two are available, one for line out and one for straight to speakers using the decks amp.
Any advice welcomed.
cheers
Brenton

Most boxster amps are in the front trunk. Likewise CD changers. There are of course cars without either. On my '01 the CD is on the left looking from the front and the amp is the middle. You have a MOST wiring system in your '04. That isn't just the simple copper wires of yore. In the states, there is an out fit that sells wiring kits and instructions (Crutchfields) and it may be worth an internet look up as that may make things easier.