Converting UK Standard Hi-Fi to US Standard Hi-Fi

I'm new to the forum but have been reading this for a while now. I'd like to know if the following was possible.

The US standard Hi-Fi differs from the UK standard Hi-Fi in that is has an additional amp and two woofers below the seats. However this amp gets its inputs from the main head unit. So in the UK if I ordered a standard Hi-Fi would I be able to connect an after market amp and run two sub-woofers from the head unit. i.e. does any one know if the head unit in the UK standard model has output for running it into an amp.

So do I take it nobody has attempted this before or nobody listens to the new kid on the block. Looking at the diagrams I found I could see that the difference between the base US and the base UK sound system is the extra amp and 2 sub-woofers below the front seats.
So the question is has anyone in the UK attempted to connect an aftermarket amp and install the speakers themselves. Surely all the space must still be there just the parts missing. Or is the head unit too different between the models.

I think the issue is we are 90% all in the US... the remaining 10% didn't see the post or just don't know...

Sorry!