I haven't yet - I'm still evaluating my gearbox expenses...
I was thinking of leaving the factory kit as-is, but building around it with some door builds and a boot box. Alternatively I could leave the rear shelf speakers alone & still wired in for the OE equipment to function, but use aftermarket replacements for the doors amped up completely seperate and the boot box.
The boot box is another problem all together though as I have a sealed box that has worked well in the past and I'm wary of trying to rebuild it for the 8's boot. The box I have is quite small, it's a 12" driver so I wouldn't lose too much space in the boot, but getting the bass through is still a problem (especially from a sealed box).
I'm still not sure - I like the idea of leaving as much of the OE stuff alone so when it comes to selling time, I can just take my stuff out and it goes to the new owner in full working order with the original kit (has always worked on past cars - much better looking un-molested than holes and wires everywhere).
The beauty of the 8 is the battery in the boot, makes things a bit easier in some respects.
For me it's time needed to solve these issues which I haven't got at the moment, but things will be changing soon, and that's what's holding me back - if my plans go accordingly, I may yet have to let go of the 8 and take a cheaper motor (one without the expensive gearbox problems
)