Yeah, the VW's are pretty good on the juice. I drive the Jetta pretty much every day and most of the time it gets driven fairly hard, but it still returns about 550-600 k's a tank. Now that's pretty good. I'm not sure what the Passat is like, given that the car is a bit bigger and the engine is a bit smaller, but I'd say its still good.
In saying all this, I still reckon that the GTR is the way to go. For most of us here, its pretty much the ultimate car and we probably wouldn't think of much else, but I guess you will get that from a Skyline forum. It all just depends on what you want the car for dude.