Looking good man! What make/model speakers are you running in the front? For an average 2 or 3 way component speaker system in the front seats you would wire a single amplified run (from the head unit or a remote amplifier) to a crossover near the front doors. The crossover separates the amplified signal into different frequencies for each speaker. From the crossover you have individual speaker wire runs for the low and/or mid range door speakers and the tweeters on each side. For the rear speakers, a lot of care stereos use coaxial 2/3-way speakers which only require 1 speaker wire run. The speakers handle all of the frequency separation with capacitors mounted onto the back of the speakers.
Below is an example setup of what I recommend on a budget.
My go to inexpensive component speakers
https://www.amazon.com/Polk-Audio-DB...tronics&sr=1-1
My go to inexpensive coaxial speakers
https://www.amazon.com/Polk-Audio-DB.../dp/B000P0PF9G
AMP - ROCKFORD FOSGATE PRIME - (I always match the amp to the impedance and power requirements of the speakers purchased)
And if you ever want to install a sub, do yourself a favor and get a kicker 10" square L5 or L7. It sounds excellent for every genre of music.. It does very well with sustained bass and punchy notes simultaneously.
https://www.amazon.com/KICKER-S10L74...tronics&sr=1-5