Baby Jogger City Mini Double! - we have one its awesome! fits through standard doorways and I have a Phil and Ted but much before this one! Also consider Mountain Buggy Duet which is coming out soon which is skinnier than the Baby Jogger City Mini Double and also I think same width as the Strider Plus which is for 2 kids.

ETA they have the new Mountain buggy on sale at Baby Village in Aust for $749 and its only 63cm in width. My BabyJogger Double is 76cm wide