Use splits the originals are put in series or parallel to show 8ohm the rears in series or parallel too I forget, look up wiring diagram.
So you can run splits fine.
Focal are good.
The doors are mid bass. Rear doors same,
In a sedan, put 6x7? in back shelf, JBL have fantastic ones in the size that fits in the cutout.
An amp up back , one for fronts.