I too like Arcade Fire.
The support act was a lad called
Jon Hopkins, to be honest I really really like/liked the trippy electronica but just thought they would have had somebody a bit more well known, for example when we went to see Radiohead they had MGMT and Bat For Lashes supporting, we all knew their songs so could have a sing along.
The NIA is a top venue to be honest, I know they change the layout though depending on the act, a tip for you, when you park in the carpark reverse in so you can drive straight out, if you need to back out you will be there for hours as nobody will let you out.
I love The Killers and agree about their new album, they will definitely do some of their old stuff though as did Coldplay.
Have a good night.