Setting up my audio

im more of a stock kinda guy i like the factory look so I have the oem infinity head unit but I wanna run an aftermarket amp and speakers,my car just a regular 4 speaker es...im more of a
N :oops: :oops: B when it comes to amps and setting this up alright so...

is the radio harness the same between the 4speaker and 7spkr?

the wiring harness from the OEM AMP what speakers is it connected to?

I read also that the speakers in the 7 spkr are 2 ohm?is that true?

as of right now i wanna put
INFINITY REFERENCE 6010cs in the front
move the infinty 6012i i have in the front towards the back and put in a basslink....