bought an 05' Frontier

So i bought an 05' Frontier SE with the nismo suspension package (I dont know what the difference between my truck and a NISMO would be) The fuel sender was bad when i bought it, and since i live in Germany i had to buy it via internet. Just got it in and changed it last night. Since i was already down there I went ahead and and did the tranny cooler bypass and changed the oil. The transmission fluid looked dirty so i called the guy i bought it from and he said he never did a flush and fill (71K miles on the truck). I seen that most of you use AMSOIL or Mobil 1 ATF, but they dont sell it here at the BX/PX. My only options are Royal Purple or Mobil multi-vehicle synthetic blend. I know that the royal purple is better, but is it really necessary? It cost over double than the mobil ATF. Please let me know your opinions.