Just as another option on a forum elsewhere on the web someone has done this:
I had Focal KRX2's installed the front and Focal 165KRC's in the rear powered by 2 x Focal FP2.350 amps. the amps fit behind behind the drawer next to the steering wheel and I can tell you the sound is out of this world.
From here:
MK7 Helix plug n play Sound System
One of the best installers in Brisbane used to be Northfeild Car Sound, i am sure they could do a similar setup. I like this design as you don't loose boot space and it would have a better front end but far more limited base (and you have to do plenty of non reversable stuff to your car.