Congratulations on the purchase!
Also sorry to hear about the circumstances leading up to it.
The Ultrex exhaust was designed to fit correctly on Australian models, so you won't have an issue with it at all.
JamieBlade recently installed one on his STI.
Tuning wise you have the option of EcuTek or Verso, both of these can be done locally.
Verso is performed by
All Star Garage, EcuTEk is performed by
Maximum Motor Sport and
Race Torque.
Both of these tuning packages use the
ECU (e.g. they rewrite settings, instead of replacing the entire unit).
The
Perth Workshops is a handy thread to bookmark!
As for the coilovers, is there a need for them?
If you are going to be constantly adjusting or changing the way the car handles then it could be a good investment and you have several brands to choose from.
It comes down to what adjustability you need and how much you would like the spend.
Otherwise you always have the choice of running a custom spring/struts package.
Hope it all works out for you