The ballasts and bulbs are different between the Xenon and the Bi Xenon, so make sure that the new lights come with these parts.
If your car is a UK car, then it will have the headlamp self levelling, so therefore 8 pin.
Cars without self levelling are 6 pin and are predominantly JDM imports.
The fixing points are the same from 2003 - 2008, so no issues there.