In your situation, I would definitely go the R34, especially if you are concerned about the "power to weight" laws (rightfully so); as according to the Police records (ie: VICroads) the R32 GTST is OVER 125kw/tonne, therefore is illegal.
Yes it's B.S. but unless you want to send $1000's in court fees, lawyers, etc., proving otherwise, you run the risk of getting done for driving an over powered car .