I agree that the 2 15" subs should be set in a sealed false floor. (But, is that enough volume to tune them @ 20Hz?
) If not, you could also put them in separate "boxes" on both sides of the trunk firing towards the trunk hatch... or slightly forward/backward.
If the amps are from the same manufacter, share the same exterior design and width, I would link them together on the same sliding rack.
Simple & clean...