the rockford fosgate system is not much of a rockford system at all, nissan just pays rockford for use of the name & rockford says nissan can sell these speakers using nissan part numbers . total rms system power is apx. 105 watts rms. 15 watts x 4 plus 45 watts for the 8" slimline sub under the drivers seat. the 420 watts you are referring to is max peak not rms . 6x9's in front doors, 6 1/2" in rear doors, if you have crew cab you have tweeters in rear doors, king cab sorry you do not get tweeters in rear doors. front door speakers are crossed over to tweeters on front dash which are 2 1/2". some speakers have nissan part numbers & some have rockford part numbers, both sell the same speakers. radio & amp is just nissan factory equipment. sound system was removed from king cab & was tested using equipment for power output of amp.