The gtr is highly respected, but the guy I bought the Stealth from had one and ended up selling it out of frustration at the high cost of getting high hp out of one compared to his friends with Mustangs and Camaros. It is a lot cheaper to get a high hp number in a large-displacement engine. He also only got 12 mpg in the gtr after upgrading the injectors and fuel supply.
I am loving the AWD twin turbo, especially on my crappy and frequently wet rural roads. It's about impossible to spin the wheels, and I don't notice much when I do, you still go straight when you peel out. I plan on upgrading the fuel supply, probably killing my mileage but oh well, speed is not cheap. With bigger injectors and pump, and the 3sx eliminator turbos already on it, the car should dyno 400+ hp to the wheels even with the power loss from the crank to all four wheels, which I think is 25%. A carbon fiber drive shaft would help lower that number; one is on my wish list. I am getting used parts cheap off of the 3si forums.