Few other things to think about.
An R34 GTR at the NEWEST is going to be what 6 years old? They really arent pratical in any way, if we are going to be 100% realistic, no 2 door car is. Not if you have friends or stuff to put places at least.
A new car is obviously new, and has a warrenty etc. More safety. But you will be reluctent to mod it more than wheels and maybe a stereo.
Also, for that sort of money, I'd be looking around a fair bit more as to what else is out there. R36 passat would spring to mind... They have more interior space, a bigger boot, more safety, more kit, awd, and better economy that either a falcon or a GTR. And resale I dare say would be better than the both as well. There are obviously other cars for that money both new and 2nd hand. I wouldn't limit yourself.