The Range Rover sub bass box is what is known as an isobaric coupled cavity design. The box has two chambers inside it, one of which is sealed and the other is 'ported' to the outside world (hence 'coupled cavity'). There are two speakers inside the box that are mounted on the wall between the two cavities, cone to cone in orientation (hence isobaric). The speakers are wired anti-phase so that they complement each other - when when is on the outward stroke the other is on the inward stroke. If you intend on using an aftermarket amplifier it is very important to remember this as wiring them incorrectly will cause them to cancell each other out.
If you look at the amplifier you will see two connector blocks. One is for the speakers, the other for the power, turn on and signal connections. The power connections can stay as they are but you will need to supply the amplifier with a switch-on signal from the head unit. This (if I recall correctly) comes in on the purple/yellow wire (pin 2 on the connector). If you originally had the top end OE stereo fitted using the Clarion amplifier (mounted also on top of the subwoofer) and it all still works with the new radio, this must still be connected at the head end. If not, you will either have to run a wire from the head unit switched out to the sub amp or locate this cable within the head unit connector at the front of the vehicle (same wiring colour).
The input signal to the amp comes in on the connector pins 1 & 5. It should be easy to identify as it will be a coaxial screened cable. You can either splice into it at the sub amp or in the original radio connector (pins 9 & 10 - black and red/yellow cables).
Hope this helps.
