Welcome to the forum.
If value for money is your main concern, buy a standard car and modify it. If you prefer the look of the mk2 Nismo buy some glasses Seriously though, the Nismos will drop further in price, but I don't personally think they will drop substantially for a few years.
The two main plus points of the Nismo are its handling, which is significantly better than the standard car, and the way it looks.
But it all really boils down to whether you must have the Nismo. If not, there are plenty of examples on this forum of people who have modded standard 370s to change handling, power and looks and who are happy with the results.
And remember that if you buy the Nismo, you'll still be needing a new exhaust. Sound wise, it's not much better than the one on the standard car.