Can you put the box in the seat and put the amp(s) on the sides of the box. And if in Street C can you put the second battery in the passenger side floor board. Thanks
You can't do anything that interferes with "normal use" of the vehicle, or make any modifications to the vehicle. So I would say box on the seat is definitely a no.
And if by "in the floor board" you mean an under vehicle battery box, those are not allowed in Street.