I have a 2002 Vogue SE with the additional speaker in the dash however only the front speakers work. I believe the amplifier must have been changed out from a lower spec one. What is the correct Amp for my car? I also note that the Alpine head units are available with two different serial numbers, does this make a difference?

It will have had the DSP amp which probably died so someone has replaced it with one from a Discovery2. That works but only on the front speakers.

When the DSP amp in my Vogue SE started failing, it was only the rear speakers that worked. It could be that your car has the right amp but it's just dropped a channel or two in the early stages of failing.

Only way to be sure is to remove it and read the numbers off it.

David.