so are you selling your gts t because you dont like the idea of losing to a wrx, 1/4 mile is priority, or you just really want a gtr?
not sure if its been covered as i just skimmed the thread, but your pretty much maxing your turbo right now, with the stock cams. Cams will bump you up to only around 280+, plus it wont run more than the 17psi your running now, maybe just 0.5psi more.
But if you like skylines, theres no better way to enjoy a skyline than in GTR form Just my 2c but i think even the older skylines are better quality than some of the late model wrx's.
your current setup is a pretty awesome street setup however! Just bear in mind that if you jump into even a light tune gtr, its gonna feel heavy and slow compared to what your in now. The gts's feel much more chuckable and responsive. I drove a 300rwkw gtr and thought what the... be prepared to spend a house making it fast and reliable.