Wow, come to Sydney - lots cheaper!
Can you please post up what was included in the quote?
To get to 300awkw if you have ceramic turbos, you'll find it doesnt cost that much, especially if you want the extra 70kw later on.
So you'd only be buying parts suited to 370kw (eg, instead of getting injectors for 300, get injectors for 370 and dont run them as hard).
Here's a bit of a list to get you started;
-New fuel pressure regulator (NISMO, Sard)
-New turbos (2860-5's)
-New front pipes, high flow cat, catback exhaust
-New air filter at least (nismo s tune one worked well for me), ARC airbox is even better
-New fuel pump (bosch 044)
-New injectors (700cc's)
-New intercooler (ARC, Nismo, Trust etc)
-New ECU (id strongly advise to get one that uses MAP vs TPS for tuning as its more cost effective compared to buying new AFM's once you max out the stockers)
-New clutch, once your stock one lets go
Thats all i can think of for now. Some people will say to not buy one thing and to buy another, but at the end of the day what you realistically want and will use the car for is what determines the shopping list of parts - also, your budget