Since both are double din sizes fitting it is not an issue. The power plug on the back may be different...Typically Nissan and other manufacturers changes their wiring harnesses every couple years so you would have to buy that years model to connect. Im not sure but i think since the newer X's come stock with fosgate systems, it may not work. The only bad thing is that if you ever wanted to upgrade to an after market headunit or speakers, you would have to do a factory amp bypass (rewiring of the speakers from the head unit) on your X.
Im pretty sure that the older X's are fine but the newer ones with the fosgate systems would require a bypass.
Sorry for blurting out crap about speakers. I work at circuit city roadshop.