Problem fixed !
My driver side rear speaker positive connector broke
and was touching the metal base and grounding out,
causing all speakers not to work.
The little tab that holds the positive and negative connectors
must've broke when I test fitted sub box.
I guess the reason the original stock stereo worked and not the others,
was because earlier in the day, I had a friend's kid fall asleep while I was
driving, so I adjusted the fade all the way to only the front speakers.