Accodring to specs, Xd cars are 50 (110lb) - 100kg (220lb) heavier than their RWD counterparts...varies by model. See here, somewhere near the end:
https://drive.google.com/open?id=1-m...7fcAp7DsHHm2hu
M6 vs A6 is 15 (33lb) - 30kg (66lb) increase:
https://drive.google.com/open?id=10-...fK48ckDHXfAqWb