im all for modding an existing engine to get more power, but you need to remember that once you start force feeding an engine and drivetrain not designed for that amount of power, reliablity comes into play.
lets say $5k for a supercharger.
another $2k for exhaust and tune.
you're looking at close to $10k and you havent even touched on engineer certificates, insurance, and other little worries with having major mods on a car. then you start ripping up clutches and gearboxes and drive shafts.
yes you'll be different, and yes you'll enjoy it (hell, I spent thousands modifying a car when I was younger.... loved it), but when you can get a v8 in the same body nice and stock (my modified car didnt have that option- it was a small hatchback), why go through all that pain?
at the end of the day, we are lucky that holden have blessed us with different powerplants in the same body shapes. my strongest advice to anyone seeking major power gains to a v6? sell it and buy a v8.
drivetrain, brakes, exhaust, engineering, insurance, roadworthyness.... all already done for you.
different story if you own a car that doesnt come with a 'powered up' option out of the dealership... but thats not the case with holden.
it'll be cheaper in the long run, and less worry. trust me.