What kind of car is this going in? I always think front loading is the best with little or no rear fill because music is only 2 channels and the bass from your subs is non-directional sound.
I had a 4 channel amp I used to run to all four channels in my Explorer. I decided to bridge to just the fronts and it was louder with the same SQ. It sounded fine from the back seats too.
Just do what fits easily and get your front soundstage as nice as possible. I would bridge or go active on the fronts and if you think its necessary run two coaxials in the back off the head unit.
I had a 4 channel amp I used to run to all four channels in my Explorer. I decided to bridge to just the fronts and it was louder with the same SQ. It sounded fine from the back seats too.
Just do what fits easily and get your front soundstage as nice as possible. I would bridge or go active on the fronts and if you think its necessary run two coaxials in the back off the head unit.