Need some help
 

i just picked up a 2009 370z and i was looking at supercharging it or twin turbo, now i got two quote for this:

HKS supercharger (installed and tuned) - $13500
Twin turbo ( installed and tuned) - $16500

Now that a big difference in price, what would i be best of getting?
And if someone could give me a short list of good places in sydney to get this done that would be great