You've thrown a spanner in the works here. I've found where you can get it for 499 but it's not in stock currently, apparently they're coming in on 30th January, and shipping would be by 5th Feb.
So here are my options as it stands:
ASUS TUF Gaming VG27AQ - 563 euro
LG 27GL850 - 524 euro (Can't get it until 5th Feb - if the dates are reliable)
LG 27GL83A-B - 514 euro
I'm guessing for the sake of 10 euro I should get the 850, although I'm being impatient and the wait will kill me
Is the Asus better than them both and worth the increase in cash?